Parasite load effects on sex ratio, size, survival and mating fitness of Heleidomermis magnapapula in Culicoides sonorensis

Heleidomermis magnapapula parasitizes the blood-feeding midge Culicoides sonorensis. Most (84%) single mermithid infective second stage juveniles (J2) developed into adult females, while parasitism by multiple J2 yielded 97% male adults. Nematodes emerged from the midge larval host as adults and mated immediately; females were ovoviviparous. Host larvae were exposed to nematode J2 and examined intact microscopically to score initial parasite load. Midge hosts were reared individually. Premature midge death, nematode survival within the host, and emerging adult nematode sex ratio and size as a function of load and host size were all tracked. Higher nematode loads produced smaller adult nematode males. The higher loads also increased and accelerated premature host death. Emergence of > 7-9 adult nematode males was rare, but up to 19 tiny males emerged from a single host. Larger midges supported higher parasite loads and a larger total volume of emerged nematode biomass. Virgin adult nematode males then were paired with females of variable, known sizes (volume) and held to determine size effects on fertility (egg hatch), and male survival (longevity). Tested adult males ranged in size from 0.0025 - 0.0334 mm3 and females from 0.0121 - 0.1110 mm3. Logistic regression indicated female nematode fertility was positively influenced by male nematode size, while nematode load and female nematode size had no significant effect. While fertility was reduced statistically in smaller males, even some of the smallest male and female individuals could be fertile. Findings are related to field studies in this system.

Hiding in Plain Sight: An Abundant and Widespread North American Horse Fly (Diptera: Tabanidae) in the Tabanus sulcifrons Group, Tabanus variegatus Fabricius, Redescribed

Tabanus variegatus F. 1805 has been called by the name Tabanus sulcifronsMacquart 1855 for over 80 yr; T. variegatus is one of the most common large horse flies attacking livestock in much of the southeastern U.S. Morphological, ecological, and molecular evidence indicates that T. variegatus is a distinct species, and we redescribe the female and describe the male. The Fabricius holotype, heavily damaged after over nearly 220 yr, is nevertheless taxonomically sound. Morphology (size, color, palp shape, and r5 wing cell shape) can usually distinguish T. variegatus from T. sulcifrons, but some specimens remain difficult to separate, especially in and west of the Mississippi River Valley. Using geometric morphometric analyses of the wing vein arrangement and palp shape the two species are significantly different. The wings of T. variegatus females also have more microsetae and sometimes a "frosty" appearance. Where they are common and sympatric, as in eastern Tennessee, they are temporally separated such that T. variegatus flies later (August-October) than T. sulcifrons (June-August), minimizing opportunity for gene flow. Museum specimens allow the approximate range of T. variegatus to be compared with that of T. sulcifrons s.l.; T. variegatus is particularly abundant from the coast of the Carolinas and Georgia east to central Tennessee and south to about central Alabama. DNA evidence (COI gene) recovers T. variegatus and T. sulcifrons s.s. in separate clades. Further studies on the T. sulcifrons complex are needed to fully resolve the range of both species, assess the degree of genetic substructuring, and examine relationships with other members of the T. sulcifrons complex.

Diagnostic applications of molecular and serological assays for bluetongue and African horse sickness

The availability of rapid, highly sensitive and specific molecular and serologic diagnostic assays, such as competitive enzyme-linked immunosorbent assay (cELISA), has expedited the diagnosis of emerging transboundary animal diseases, including bluetongue (BT) and African horse sickness (AHS), and facilitated more thorough characterisation of their epidemiology. The development of assays based on real-time, reverse-transcription polymerase chain reaction (RT-PCR) to detect and identify the numerous serotypes of BT virus (BTV) and AHS virus (AHSV) has aided in-depth studies of the epidemiology of BTV infection in California and AHSV infection in South Africa. The subsequent evaluation of pan-serotype, real-time, RT-PCR-positive samples through the use of serotype-specific RT-PCR assays allows the rapid identification of virus serotypes, reducing the need for expensive and time-consuming conventional methods, such as virus isolation and serotype-specific virus neutralisation assays. These molecular assays and cELISA platforms provide tools that have enhanced epidemiologic surveillance strategies and improved our understanding of potentially altered Culicoides midge behaviour when infected with BTV. They have also supported the detection of subclinical AHSV infection of vaccinated horses in South Africa. Moreover, in conjunction with whole genome sequence analysis, these tests have clarified that the mechanism behind recent outbreaks of AHS in the AHS-controlled area of South Africa was the result of the reversion to virulence and/or genome reassortment of live attenuated vaccine viruses. This review focuses on the use of contemporary molecular diagnostic assays in the context of recent epidemiologic studies and explores their advantages over historic virus isolation and serologic techniques.

Collecting and Monitoring for Northern Fowl Mite (Acari: Macronyssidae) and Poultry Red Mite (Acari: Dermanyssidae) in Poultry Systems

The two most economically important poultry ectoparasites are the northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), and the poultry red mite, Dermanyssus gallinae (De Geer). Both mites are obligate blood feeders but differ in where they reside. Sampling methods thus focus on-host, especially the vent feathers, for northern fowl mite and off-host, especially cracks and crevices near the nighttime roosting areas, for poultry red mite. Much remains unknown, however, about the basic biology and ecology of both mites. Here we discuss mite detection, quantification, and decision making and provide thoughts on future directions for research.

Genetic Structure of Northern Fowl Mite (Mesostigmata: Macronyssidae) Populations Among Layer Chicken Flocks and Local House Sparrows (Passeriformes: Passeridae)

The northern fowl mite (NFM) Ornithonyssus sylviarum Canestrini and Fanzago is a blood-feeding ectoparasite found on many wild bird species and is a pest of poultry in the United States. It is unknown where NFM infestations of poultry originate, which has made it difficult to establish preventative biosecurity or effective control. We used microsatellite markers to evaluate genetic variation within and among NFM populations to determine routes of introduction onto farms and long-term persistence. We compared NFM from flocks of chickens (Gallus gallus) on different farms in California, Washington, and Georgia, and we compared NFM collected over a 5-yr interval. On three farms we collected NFM from chickens and house sparrows (Passer domesticus) nesting on each farm, which we used to assess movement between host species. There was strong genetic structure among mites from different poultry farms and low estimates of migration between farms. There were significant differences between mites on chickens and house sparrows on two farms where sparrows nested near flocks, indicating no exchange of mites. Only one farm showed evidence of NFM movement between chickens and sparrows. There was high genetic similarity between mites collected 5 yr apart on each of two farms, indicating that NFM infestations can persist for long periods. The genetic patterns did not reveal sources of NFM infestations on chicken farms. The data suggest that NFMs are strongly differentiated, which likely reflects periodic population declines with flock turnover and pesticide pressure.

Sex Ratios and Mating Status of the Horn Fly on Pastured Cattle as a Function of Repellent-Oil Treatments

Haematobia irritans (L.) (Diptera: Muscidae) were netted from pastured cattle in California over two summers, with the goal of documenting on-host sex ratios and mating success as they might vary with repellent applications. Sex ratios were calculated from 100 adults per herd per date, and mating status of females (n = 30 per herd per date) was assessed by dissection of spermathecae. Flies were collected before, during, and after 2-wk treatment periods with each of two repellent-oil mixtures: a 15% mixture of fatty acids (C8, C9, C10) in mineral oil or a 2% solution of geraniol in mineral oil. During the treatment period, flies were collected 3-4 d after the prior treatment and immediately before the next treatment. A separate herd used in the second year was untreated. Overall, the proportion female was 0.65 ± 0.01 (mean ± SE) (range 0.28-0.81). Sex ratios were not altered over time by treatments with either repellent. Overall, proportion of females mated was 0.744 ± 0.018 (range 0.40-1.00). Mating status was significantly affected by the two repellent treatments, which did not differ from each other. For treatment herds, proportion mated before treatment was 0.789 ± 0.039, dropping significantly to 0.659 ± 0.038 during the treatment period, and rebounding to 0.750 ± 0.035 after treatments ceased. Treatments probably killed or repelled the existing heterogeneous fly population, and during treatment relatively more flies were unmated recent arrivals.

Egg and Larval Morphology of Culicoides sonorensis (Diptera: Ceratopogonidae)

The egg and larval instars (L1-L4) of Culicoides sonorensis Wirth and Jones are described. Average (range) of body lengths of a laboratory colony (Van Ryn) were 0.45 (0.43-0.48) mm for eggs, 0.72 (0.39-0.92) mm for L1, 1.8 (1.3-2.2) mm for L2, 3.6 (2.2-5.0) mm for L3, and 5.9 (5.0-6.9) mm for L4. Head capsule lengths were 0.067 (0.064-0.070) mm for L1, 0.100 (0.094-0.110) for L2, 0.157 (0.144-0.168) for L3, and 0.316 (0.300-0.324) mm for L4. Wild and colony L4 larvae differed in many standard metrics such as head length or width, but head ratios and pharyngeal armature measurements were comparable. Standard external and internal features of the head capsule are described. Scanning electron microscope photos revealed pharyngeal armature structure was similar for L2-L4. The pharyngeal armature and piercing mandibles suggest a generalist feeder and opportunistic predator. Egg ansullae were randomly distributed (as opposed to rows in most other Culicoides spp.) and averaged 1.98 ansullae per 25 µm2 of egg surface. Ansullae were widened and porous apically, averaging 1.29 microns long, 0.65 µm at the base, and 1.06 µm at the apex. Only the L1 had a proleg, structurally complex, and featuring five rows of posteriorily directed, shorter spines (1-3 µm long) and 8-10 setae 18 µm long with hooked tips. On terrestrial mud, this proleg was used for surface crawling, and the L1 navigated dry conditions better than the more aquatic L2-L4 stages. Eggs are laid above waterline, and the L1 proleg is probably an advantage in terrestrial surface movement.

Evaluation of Two Entomopathogenic Fungi for Control of Culex quinquefasciatus (Diptera: Culicidae) in Underground Storm Drains in the Coachella Valley, California, United States

Commercially available formulations of two entomopathogenic fungi, Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Clavicipitaceae) and Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae), were assessed for control of Culex quinquefasciatus Say (Diptera: Culicidae) in underground storm drain systems (USDS) in the Coachella Valley of southern California. Each of three treatments, the two fungi or a water control, was applied to 1 m2 of vertical wall at eight USDS sites in spring and autumn of 2015. Fungal infectivity and lethality were assessed at 1 d and 1, 2, and 4 wk post-application. Overnight bioassays using adult lab-reared female mosquitoes were carried out on the treated USDS wall areas and then mosquitoes were held in the laboratory for up to 21 d to allow fungal infections to be expressed. Postmortem fungal sporulation was assessed up to 2 wk at 100% humidity. Mosquito-fungal interactions also were assessed in bioassays of the three treatments on filter paper exposed to USDS conditions during autumn. Metarhizium anisopliae killed mosquitoes faster than B. bassiana; nevertheless, both freshly applied formulations caused greater than 80% mortality. Fungal persistence declined significantly after 1 wk under USDS conditions, but some infectivity persisted for more than 4 wk. Beauveria bassiana was more effective against Cx. qinquefasciatus in the spring, while M. anisopliae was more effective in the cooler conditions during autumn. USDS environmental conditions (e.g., temperature, relative humidity, standing water) influenced fungal-related mortality and infection of Cx. quinquefasciatus. The utility of these fungal formulations for mosquito abatement in the Coachella Valley and implications for fungal control agents in USDS environments are discussed.

Longevity of Fly Baits Exposed to Field Conditions

Insecticidal fly baits are important tools for adult house fly, Musca domestica L. (Diptera: Muscidae), control, especially on animal operations. Two house fly baits, containing either cyantraniliprole or dinotefuran, were tested on a dairy farm for attractiveness over time compared to a sugar control. Sticky trap and bucket trap house fly catches were recorded for each bait type at 1 h, 3 h, 6 h, 12 h, 24 h, 48 h, 72 h, and 168 h. After 1 wk of exposure to flies and field conditions, these 'aged' baits were tested against fresh baits for fly visitation in the field over 1 h. House flies from each bait type (aged and fresh) were collected and kept under laboratory conditions to assess mortality over 3 d. Average visitation of individual flies to each bait type (fresh) in the field was also evaluated. Sticky traps did not show significant fly catch differences among bait types over time, however bucket trap catches did show significant differences for cyantraniliprole bait and dinotefuran bait compared to sugar at 72 h and 168 h. No significant differences among fly visitation to aged or fresh baits were found. Fresh cyantraniliprole bait and dinotefuran bait resulted in greater fly mortality compared to controls, but not compared to aged toxic baits. Average house fly visitation time was greatest for sugar and cyantraniliprole bait.

The Dark Side of Light Traps

Light-baited suction traps are one of the most widely used tools for vector surveillance. Their popularity stems from ease of use even in remote locations, range and abundance of species caught, and low cost. The availability of smaller, portable models, like the CDC miniature light trap, have further increased their ubiquity in entomological field studies. However, when researchers have looked, light trap collections are usually biased in ways that may affect data interpretation for epidemiological studies. If used alone, light traps may fail to collect important or infected vectors, and light traps are inefficient or ineffective when competing ambient light is present. In this article, we discuss these biases and limitations in terms of their effect on collection efficiency, population data, and pathogen detection. While light trap data certainly have a purpose, an over-reliance on light trapping risks drawing false conclusions about vector populations and vector-borne disease epidemiology. These concerns are especially troubling when light trap data are used to inform policy decisions meant to protect human and animal health. Particularly when a species' response to light is unknown or poorly characterized, light traps should be used in conjunction with supplemental sampling methods. Researchers conducting vector surveillance field studies should carefully consider their study design and objectives when deciding on a trapping method or methods, and specifically endeavor to understand the limitations of their data. Only then can researchers take advantage of the best attributes of light traps while avoiding their dark side.

Effects of Fatty Acid and Geraniol Repellent-Oil Mixtures Applied to Cattle on Blood Feeding and Reproductive Parameters in Field Populations of Haematobia irritans (Diptera: Muscidae)

California pastured cattle were treated with 250 ml of a 15% mixture of fatty acids (C8-C9-C10) or 125 ml of 2% geraniol in a mineral oil carrier to assess impacts on horn flies, Haematobia irritans (L.) (Diptera: Muscidae) over two summers. Horn flies were netted from cattle every 3-4 d for 2 wk before treatment, 2 wk during treatment (four treatments, with flies collected before each treatment), and 2 wk after treatments ceased. Blood meal weights were estimated by hemoglobin assay of excised abdomens. Other females were dissected to determine the number of active ovarioles and the stage of primary follicle development. Depending on year and herd, pretreatment males contained an average of 0.6-1.0 mg of blood, while females contained 1.7-2.7 mg. Pretreatment egg development (least developed oocytes were stage 1 and fully developed eggs were stage 5) averaged 3.7-4.3, and number of active ovarioles averaged 18.1 to 19.6/female. During treatment periods, significant reductions in blood weight were noted for females, but usually not for males, and females also often exhibited reduced mean oocyte stage and number of active ovarioles. Peaks in proportions of young nulliparous females (oocyte stages 1 or 2) were seen during some repellent application periods. This suggested older females had been killed or driven off from the local population by the treatments, and flies on cattle included more young flies that likely were recent arrivals. The repellent-oil mixture thus impacted blood feeding, reproductive fitness, and probably age structure in the field.

Field Distribution and Density of Culicoides sonorensis (Diptera: Ceratopogonidae) Eggs in Dairy Wastewater Habitats

Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae) is a key bluetongue virus vector in the United States. Immatures occur in mud near the edges of wastewater ponds and are understudied targets for control efforts. Eggs of C. sonorensis were collected in the morning from a dairy wastewater pond bank by taking 5-ml surface mud samples along four transects on each of six dates. Surface mud samples parallel to waterline (10-cm long, 1-cm wide, and 0.5-cm deep) were removed at 5-cm increments ranging from 15 cm below waterline up to 25 cm above waterline. Eggs were removed using MgSO4 flotation, held on moist filter paper, and scored for hatching over 3 d. Eggs hatching on days 2 and 3 were assumed to have been laid on the test night. Water levels were stable within a night according to time-lapse camera photos. Most samples from below the waterline had no eggs and were not analyzed statistically. Mean (±SE) sample moisture (25.8 ± 2.1 at 5 cm above waterline and 19.8 ± 2.6% at 25 cm above waterline) did not vary significantly by position above waterline. The highest density of viable eggs (21 eggs/5 ml), proportion of mud samples positive for viable eggs (75%), and proportion of eggs hatching (80%) were found 5 cm above waterline. Oviposition in the few hours after sunset is adaptive, allowing eggs to age, develop the serosal cuticle, and resist later desiccation. As a potential control method, reducing water levels after midnight would encourage young egg desiccation.

A review of the biology, ecology, and control of the northern fowl mite, Ornithonyssus sylviarum (Acari: Macronyssidae)

The northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago, 1877), is found on several continents and has been a major pest of poultry in the United States for nearly a century. Lack of earlier USA reports in the United States suggests an introduction or change to pest status in domestic poultry systems occurred in the early 1900s. Though predominantly a nest-parasite of wild birds, this obligate hematophagous mite is a permanent ectoparasite on domestic birds, especially egg-laying chickens. Economic damage is incurred by direct blood feeding and activation of the of host's immune responses. This in turn causes decreased egg production and feed conversion efficiency, and severe infestations can cause anemia or death to birds. Here we review the biology, ecology, and recent control measures for the northern fowl mite. Photomicrographs are included of adult males and females, protonymphs, and larvae with key characters indicated. Special emphasis is placed on current knowledge gaps of basic and applied science importance.

Hovering and Swarming Behavior of Male Tabanus calens (Diptera: Tabanidae) in Tennessee and New Jersey, USA

Hovering and swarming activity of male Tabanus calens L. were documented at distinctive sites above a woodland road clearing in Knox Co., TN (7 d), and above a slow-flowing river in Morris Co., NJ (6 d). Activity was restricted to the period near sunset. Mean activity typically began about 10 min before sunset and continued until about 10 min after sunset, with an average duration of 18.7 min (Tennessee) and 20.8 min (New Jersey). Swarming began earlier and thus lasted longer (55 min) on one cool New Jersey date. Onset and particularly cessation of activity tended to be statistically correlated with sunset time. Most males hovered at heights of 5-8 m in Tennessee, and they hovered in stable locations for a median of only 10 s (maximum 2 min 57 s) before darting away. Hovering in New Jersey was observed from 0.5-8.0 m above the water. The behavior of T. calens might be especially interesting to study in more detail, given its unusual eye morphology (lack of obvious dorsoventral facet size differences found in males of most other Tabanidae).

Comparative in vitro evaluation of contact activity of fluralaner, spinosad, phoxim, propoxur, permethrin and deltamethrin against the northern fowl mite, Ornithonyssus sylviarum

Background

Northern fowl mites (Ornithonyssus sylviarum) are obligate hematophagous ectoparasites of both feral birds and poultry, particularly chicken layers and breeders. They complete their entire life-cycle on infested birds while feeding on blood. Infestations of O. sylviarum are difficult to control and resistance to some chemical classes of acaricides is a growing concern. The contact susceptibility of O. sylviarum to a new active ingredient, fluralaner, was evaluated, as well as other compounds representative of the main chemical classes commonly used to control poultry mite infestations in Europe and the USA.

Methods

Six acaricides (fluralaner, spinosad, phoxim, propoxur, permethrin, deltamethrin) were dissolved and serially diluted in butanol:olive oil (1:1) to obtain test solutions used for impregnation of filter paper packets. A carrier-only control was included. Thirty adult northern fowl mites, freshly collected from untreated host chickens, were inserted into each packet for continuous compound exposure. Mite mortality was assessed after incubation of the test packets for 48 h at 75% relative humidity and a temperature of 22 °C.

Results

Adult mite LC₅₀ /LC₉₉ values were 2.95/8.09 ppm for fluralaner, 1587/3123 ppm for spinosad, 420/750 ppm for phoxim and 86/181 ppm for propoxur. Permethrin and deltamethrin LC values could not be calculated due to lack of mortality observed even at 1000 ppm.

Conclusions

Northern fowl mites were highly sensitive to fluralaner after contact exposure. They were moderately sensitive to phoxim and propoxur, and less sensitive to spinosad. Furthermore, the tested mite population appeared to be resistant to the pyrethroids, permethrin and deltamethrin, despite not being exposed to acaricides for at least 10 years.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2289-z) contains supplementary material, which is available to authorized users.

Low Temperature Tolerance of Culicoides sonorensis (Diptera: Ceratopogonidae) Eggs, Larvae, and Pupae From Temperate and Subtropical Climates

Culicoides sonorensis Wirth and Jones biting midges are the primary North American vectors of bluetongue virus (BTV), which infects domestic ruminant livestock and can cause high morbidity and mortality. Both virus and vector exhibit highly seasonal activity patterns, even in subtropical climates like southern California. However, the exact mechanism of BTV and Culicoides overwintering has been debated. In this study, we examined the supercooling point (SCP) and lower lethal temperature of a laboratory colony of C. sonorensis eggs, larvae, and pupae, as well as of field-collected larvae and pupae from subtropical (California) and temperate (Colorado) climates. Larvae and pupae succumbed to temperatures higher than their respective SCPs, indicating death from prefreezing cold injury. Eggs were the most cold-tolerant life stage, and were able to tolerate 1-h exposures to temperatures as low as -20 °C without suffering complete mortality. Larvae were the least cold-tolerant life stage and suffered complete mortality at < -4 °C, while temperatures of -9 to -10 °C were required to kill all pupae. Larvae and embryos suffered chronic cold injury after exposure to subzero temperatures, which increased mortality. Field-collected larvae succumbed to slightly higher temperatures ( > -3 °C) than colony larvae, but did not differ significantly in their survival. Culicoides sonorensis immatures did not cold harden when exposed to 4 °C for 24 h before freezing. Results of this study indicate that C. sonorensis eggs are more tolerant of environmental stress than previously thought. Further work is needed on C. sonorensis winter survival in the field to corroborate laboratory studies.

Progress and knowledge gaps in Culicoides ecology and control

The Bluetongue and Schmallenberg virus outbreaks in Europe between 1999 and 2013 stimulated progress in Culicoides field ecology and control. In responding to these outbreaks, however, the deficit of broadly trained entomologists became evident. Culicoides research has been uneven, and critical gaps remain in our knowledge of vector ecology. Certain aspects of adult midge biology have gotten more attention (biting rates and relationship to trap collections, seasonal activity and survey, taxonomy of critical species complexes). Some aspects of adult midge biology (survival, resting site selection, or direct dispersal measurements) have been understudied. More work is needed on Culicoides immatures (taxonomy and details of ecology). Control research has centred on insecticide treatments applied to animals. However, our true goal is not vector control, but reducing disease agent transmission. We require field vector control targets (e.g. how far we might need to reduce biting rates) needed to interrupt transmission. The most critical need is for studies incorporating vector control experimentally into epidemiological studies in active arbovirus transmission zones. Such field interdisciplinary studies are absolutely required to understand transmission dynamics. Through the power of experimental field studies, we should be able to develop both theoretical and operational guidelines for disease management.

Timing Diatomaceous Earth-Filled Dustbox Use for Management of Northern Fowl Mites (Acari: Macronyssidae) in Cage-Free Poultry Systems

Northern fowl mite management on conventionally caged birds relies on synthetic pesticide sprays to wet the vent. Cage-free chickens cannot be effectively treated this way, and pesticide use is restricted in organic production. Dustbathing behavior is encouraged in newer production systems for increased hen welfare. Diatomaceous earth (DE) is an approved organic insecticide that can be mixed with sand in dustboxes, suppressing mites but not excluding them, and potentially allowing development of mite immunity. We tested two hypotheses: 1) that DE-filled dustboxes placed before northern fowl mite introduction (prophylactic use) prevents mite populations from reaching economically damaging thresholds, and 2) that bird exposure to low mite numbers allows for protective hen immunity to develop and suppress mites after dustboxes are removed. We also tested if different beak trimming techniques (a commercial practice) affect mite growth. Mites were introduced to birds after dustboxes were made available. Average mite densities in flocks remained below damaging levels while dustboxes were available. Average mite populations rebounded after dustbox removal (even though DE persisted in the environment) regardless of the timing of removal. Mite densities on birds where a traditional hot-blade beak trimming technique was used (trial 1) were high. Mite densities in trial 2, where a newer precision infra-red trimming was used, were lower. The newer infra-red trimming method resulted in nearly intact beaks, which were better for mite control by bird grooming behaviors. The combination of early dustbox use and infra-red beak trimming should allow producers to avoid most mite damage in cage-free flocks.

Sulfur Dust Bag: A Novel Technique for Ectoparasite Control in Poultry Systems

Animal welfare-driven legislation and consumer demand are changing how laying chickens are housed, thus creating challenges for ectoparasite control. Hens housed in suspended wire cages (battery cages) are usually treated with high-pressure pesticides. This application type is difficult in enriched-cage or cage-free production. Alternatives to pesticide sprays are needed in enriched-cage or cage-free systems. In this study, we tested the efficacy of sulfur dust deployed in "dust bags" for control against the northern fowl mite (Ornithonyssus sylviarum), which causes host stress, decreased egg production, and reduced feed conversion efficiency. Dust bags were hung from the tops of cages or were clipped to the inside front of cages. We also tested permethrin-impregnated plastic strips, marketed for ectoparasite control in caged or cage-free commercial and backyard flocks. Previous work has shown sulfur to be very active against poultry ectoparasites; however, we found that the placement of bags was important for mite control. Sulfur in hanging bags reduced mites on treatment birds by 95 or 97% (depending on trial) within one week of being deployed, and mite counts on these birds were zero after 2 wk. Clipped sulfur bags acted more slowly and did not significantly reduce mites in one trial, but reduced mite counts to zero after 4 wk in trial 2. Permethrin strips had no effect on mite populations. This may have been due to mite resistance, even though this mite population had not been exposed to pyrethroids for several years. Sulfur bags should be effective in caged or cage-free systems.

Trap placement and attractant choice affect capture and create sex and parity biases in collections of the biting midge, Culicoides sonorensis

Culicoides sonorensis Wirth & Jones (Diptera: Ceratopogonidae) is the primary North American vector of bluetongue virus (BTV), which can cause high morbidity and mortality in ruminant livestock or wildlife. Worldwide, most Culicoides surveillance relies on light (usually UV) traps typically placed near animals or larval development sites. However, the trapping method can cause sex, species and parity biases in collections. We collected C. sonorensis from three dairies in California using suction traps baited with CO2 , UV light or CO2  + UV placed near animals, wastewater ponds, or in fields. Higher numbers of parous females were collected using CO2  + UV traps, although this difference was only significant on one dairy. UV traps were poor at collecting nulliparous females, but the addition of UV to a trap increased the abundance of males in a collection. Traps set in open fields collected significantly higher numbers of males and females than in either of the other two locations. In some cases, there was a significant interaction between the trap type and site. We discuss the limitations of traditional trapping methodologies for C. sonorensis and make suggestions for vector surveillance.

Dividing the pie: differential dung pat size utilization by sympatric Haematobia irritans and Musca autumnalis

Horn flies [Haematobia irritans (Diptera: Muscidae) (L.)] and face flies [Musca autumnalis (Diptera: Muscidae) De Geer] use the same larval resource, but their interactions are poorly studied. Dung pats (n = 350) were core sampled in the summers of 2012 and 2013 from irrigated pastures in Pomona, California, U.S.A. (34°03'N, 117°48'W) and held for face fly and horn fly emergence. Surface areas and estimated weights were recorded for each whole pat. Almost half (42.0%) of the pat cores yielded neither fly, 29.7% yielded horn flies only, 12.9% yielded face flies only and 15.4% yielded both flies. Of the fly-positive pats, surface area and mass were larger for face fly-occupied pats, whereas horn fly-occupied pats were smaller. Pats shared by the two species were intermediate. Horn flies per positive core were unaffected by the absence/presence of face flies, but half as many face flies emerged when pats were co-inhabited by horn flies. Face flies inhabited larger pats, which might better resist heating and drying, to which they are susceptible; horn flies inhabited a broad pat size range. Horn fly tolerance of lower dung moisture probably allows horn flies to colonize and survive in a wide range of pats in dry areas like southern California.

Northern fowl mite (Ornithonyssus sylviarum) effects on metabolism, body temperatures, skin condition, and egg production as a function of hen MHC haplotype

The northern fowl mite, Ornithonyssus sylviarum, is the most damaging ectoparasite on egg-laying hens in the United States. One potential strategy for management is breeding for mite resistance. Genes of white leghorn chickens linked to the major histocompatibility complex (MHC) were previously identified as conferring more (B21 haplotype) or less (B15 haplotype) mite resistance. However, immune responses can be energetically costly to the host and affect the economic damage incurred from mite infestations. We tested energy costs (resting metabolic rate) of mite infestations on egg-laying birds of both MHC B-haplotypes. Resting metabolic rates were documented before (pre-) mite infestation, during (mid-) infestation, and after peak (late) mite infestation. Mite scores, economic parameters (egg production, feed consumption), and physiological aspects such as skin inflammation and skin temperature were recorded weekly. Across experiments and different infestation time points, resting metabolic rates generally were not affected by mite infestation or haplotype, although there were instances of lower metabolic rates in infested versus control hens. Skin temperatures were recorded both at the site of mite feeding damage (vent) and under the wing (no mites), which possibly would reflect a systemic fever response. Ambient temperatures modified skin surface temperature, which generally was not affected by mites or haplotype. Feed conversion efficiency was significantly worse (4.9 to 17.0% depending on trial) in birds infested with mites. Overall egg production and average egg weight were not affected significantly, although there was a trend toward reduced egg production (2 to 8%) by infested hens. The MHC haplotype significantly affected vent skin inflammation. Birds with the mite-resistant B21 haplotype showed earlier onset of inflammation, but a reduced overall area of inflammation compared to mite-susceptible B15 birds. No significant differences in resting energy expenditure related to mite infestation or immune responses were detected. Potential breeding for resistance to mite infestation using these two haplotypes appears to be neutral in terms of impact on hen energy costs or production efficiency, and may be an attractive option for future mite control.

Diversity and Prevalence of Ectoparasites on Backyard Chicken Flocks in California

Peridomestic ("backyard") chicken flocks are gaining popularity in the developed world (e.g., North America or Europe), yet little is known regarding prevalence or severity of their ectoparasites. Therefore, five birds on each of 20 properties throughout southern California were surveyed in summer for on-host (permanent) and off-host dwelling (temporary) ectoparasites. Only four premises (20%) were entirely free of ectoparasites. In declining order of prevalence (% of premises), permanent ectoparasites included six chicken louse species: Menacanthus stramineus (Nitzsch) (50%), Goniocotes gallinae (De Geer) (35%), Lipeurus caponis (L.) (20%), Menopon gallinae (L.) (15%), Menacanthus cornutus (Schömmer) (5%), and Cuclotogaster heterographus (Nitzsch) (5%). Only one flea species, Echidnophaga gallinacea (Westwood) (20%), was found. Three parasitic mite species were observed: Ornithonyssus sylviarum (Canestrini & Fanzago) (15%), Knemidocoptes mutans (Robin & Lanquetin) (10%), and Dermanyssus gallinae (De Geer) (5%). Many infestations consisted of a few to a dozen individuals per bird, but M. stramineus, G. gallinae, M. cornutus, and E. gallinacea were abundant (dozens to hundreds of individuals) on some birds, and damage by K. mutans was severe on two premises. Off-host dwelling ectoparasites were rare (D. gallinae) or absent (Cimex lectularius L., Argasidae). Parasite diversity in peridomestic flocks greatly exceeds that is routinely observed on commercial chicken flocks and highlights a need for increased biosecurity and development of ectoparasite control options for homeowners.

Estimating Field Densities of Haematobia irritans (Diptera: Muscidae) Using Direct Visual Field Counts Versus Photographic Assessments

Horn flies, Haematobia irritans (L.), were photographed on cattle and then immediately estimated visually in the field on pastured beef cattle in southern California. Horn flies were counted in the pictures later on a computer screen. For 479 counts on individual cattle, the concordance correlation coefficient between the visual and photo-based assessments was 0.790, but was better for the higher half of the counts (0.732) than for the lower half of the counts (0.217). Major axis regression indicated that visual estimates were consistently higher than the number of flies counted in the pictures across the entire density range. Based on average raw means, the visual estimates averaged 21% higher than the photo counts. Visual estimates included flies on the belly and lower legs that could not be seen in a photo, and lower densities may have been more susceptible to such error. Where flies can be seen well, e.g. for very tame animals, the visual estimates were much faster and more cost-efficient and were sufficient to track relative horn fly abundance changes.

Management of North American Culicoides Biting Midges: Current Knowledge and Research Needs

Culicoides biting midges (Diptera: Ceratopogonidae) are biological vectors of two important viruses impacting North American ruminants--bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV). These viruses have been identified for over 60 years in North America, but we still lack an adequate understanding of the basic biology and ecology of the confirmed vector, Culicoides sonorensis, and know even less about other putative Culicoides vector species. The major gaps in our knowledge of the biology of Culicoides midges are broad and include an understanding of the ecology of juveniles, the identity of potential alternate vector species, interactions of midges with both pathogens and vertebrates, and the effectiveness of potential control measures. Due to these broad and numerous fundamental knowledge gaps, vector biologists and livestock producers are left with few options to respond to or understand outbreaks of EHD or BT in North America, or respond to emerging or exotic Culicoides-transmitted pathogens. Here we outline current knowledge of vector ecology and control tactics for North American Culicoides species, and delineate research recommendations aimed to fill knowledge gaps.

Seasonality and Diapause of Musca autumnalis (Diptera: Muscidae) at its Southern Limits in North America, With Observations on Haematobia irritans (Diptera: Muscidae)

The face fly (Musca autumnalis De Geer) and horn fly (Haematobia irritans ([L.])) were studied at the southern edge of the face fly's North American range, examining southern California geographic distribution, seasonal activity on cattle and in dung, and diapause. Face flies were common only at Pomona (34°03'N, 117°48'W). Other irrigated pastures, even those only slightly inland from Pomona, were probably too warm for face flies, due to a steep west (cooler) to east (warmer) temperature gradient. Horn flies were abundant at all sites. Adult densities on cattle, adults emerging from dung pats, and prevalence of fly-positive pats were assessed for both fly species throughout a year at Pomona. Summer adult horn fly densities of 500-2,000 flies per cow, or face fly densities of 3-10 flies per face, were common. Summer prevalence of face fly-positive pats and horn fly-positive pats was about 20-40% and 30-70%, respectively. Face fly adults diapaused from late October until late March and early April. Horn flies probably diapaused as pupae from late October or early November to early-mid March, although some emerged in winter. Experimental cohorts of October-emerging adult face flies were held in a representative overwintering site. They exhibited hypertrophied fat body and undeveloped oocytes, which are characteristics of diapause, and survived until the following spring. The dominant diapause cues in face and horn flies are probably photoperiod and temperature. Despite warm winter temperatures that would permit activity of both species, and despite relatively long winter day lengths, face flies and most horn flies still diapaused at this latitude.

Bluetongue virus infection creates light averse Culicoides vectors and serious errors in transmission risk estimates

BACKGROUND

Pathogen manipulation of host behavior can greatly impact vector-borne disease transmission, but almost no attention has been paid to how it affects disease surveillance. Bluetongue virus (BTV), transmitted by Culicoides biting midges, is a serious disease of ruminant livestock that can cause high morbidity and mortality and significant economic losses. Worldwide, the majority of surveillance for Culicoides to assess BTV transmission risk is done using UV-light traps. Here we show that field infection rates of BTV are significantly lower in midge vectors collected using traps baited with UV light versus a host cue (CO2).

METHODS

We collected Culicoides sonorensis midges in suction traps baited with CO2, UV-light, or CO2 + UV on three dairies in southern California to assess differences in the resulting estimated infection rates from these collections. Pools of midges were tested for BTV by qRT-PCR, and maximum likelihood estimates of infection rate were calculated by trap. Infection rate estimates were also calculated by trapping site within a dairy. Colonized C. sonorensis were orally infected with BTV, and infection of the structures of the compound eye was examined using structured illumination microscopy.

RESULTS

UV traps failed entirely to detect virus both early and late in the transmission season, and underestimated virus prevalence by as much as 8.5-fold. CO2 + UV traps also had significantly lower infection rates than CO2-only traps, suggesting that light may repel infected vectors. We found very high virus levels in the eyes of infected midges, possibly causing altered vision or light perception. Collecting location also greatly impacts our perception of virus activity.

CONCLUSIONS

Because the majority of global vector surveillance for bluetongue uses only light-trapping, transmission risk estimates based on these collections are likely severely understated. Where national surveillance programs exist, alternatives to light-trapping should be considered. More broadly, disseminated infections of many arboviruses include infections in vectors' eyes and nervous tissues, and this may be causing unanticipated behavioral effects. Field demonstrations of pathogen-induced changes in vector behavior are quite rare, but should be studied in more systems to accurately predict vector-borne disease transmission.

Relationships between beak condition, preening behavior and ectoparasite infestation levels in laying hens

The effects of beak condition on ectoparasite populations and preening in laying hens were investigated. Beak-trimmed and beak-intact caged Hy-Line W-36 hens were infested with either chicken body lice or northern fowl mites using a 2×2 factorial design with 4 replicate cages (each containing 2 hens)/treatment: 1) BTL: (beak-trimmed lice-infested); 2) BTM: (beak-trimmed mite-infested); 3) BIL: (beak-intact lice-infested); and 4) BIM: (beak-intact mite-infested). Mite scores and lice numbers were estimated weekly. Hens were video recorded the wk before infestation and at wk 6 and 9 post-infestation. Time spent preening on 6 body areas and in total were analyzed using a repeated measures ANOVA. There was a wk×beak condition interaction for lice loads, with BTL harboring approximately 17 times more lice than BIL from wk 7 to 10 post-infestation (P<0.0001). Beak condition affected mite loads (P<0.0001), with BTM having a higher mite score (3.8±0.26) than BIM (1.4±0.26). At peak infestation, BTL spent more total time preening (P=0.02, s±SE: 232.1±37.6) than prior to infestation (33.9±37.6) and directed their preening behavior towards the vent. In contrast, BIL (73.9±37.6), BTM (9.4±1.6), and BIM (8.6±1.6) did not increase total time spent preening over pre-infestation levels (103.6±37.6, 5.8±1.6, 6.7±1.6 respectively), although BTM did redirect their preening behavior toward the vent. This study confirmed previous studies showing that an intact beak is important for reducing ectoparasite infestations. Preening behavior increased in response to lice infestation, but only in beak-trimmed hens; preening behavior and louse load were correlated at peak infestation. In contrast, mite infestation did not lead to increased preening, and there was no correlation between preening and mite load. However, both lice- and mite-infested hens directed preening behavior predominantly towards the vent where these parasites are typically found.

Laboratory and field assessment of cyantraniliprole relative to existing fly baits

BACKGROUND

Toxic fly baits are commonly used for fly control in California animal operations. However, resistance development has been a problem. Comprehensive laboratory and field studies were conducted to test commercial baits (imidacloprid, methomyl, dinotefuran, spinosad) and one novel cyantraniliprole bait. A susceptible Musca domestica strain was compared with wild-type M. domestica and Fannia canicularis strains in the laboratory using choice/no-choice tests. Field visitation to baits and both short- and longer-term mortality were documented.

RESULTS

Susceptible Musca suffered high mortality with all baits after 3 days of choice and no-choice tests. Wild-type Musca mortality was more variable and higher in no-choice relative to choice tests. Fannia were most susceptible to spinosad > dinotefuran = cyantraniliprole > methomyl = imidacloprid. Field Musca were most attracted to spinosad > cyantraniliprole > dinotefuran > sugar > methomyl > imidacloprid. Delayed mortality from bait-fed field flies (captured and held with untreated food and water for 3 days) was ranked spinosad = cyantraniliprole > dinotefuran = methomyl > imidacloprid > sugar.

CONCLUSION

Behavioral resistance of M. domestica to imidacloprid and methomyl persists. Spinosad and cyantraniliprole baits (delayed mortality) performed best. Speed of action may be a factor in use and misuse of baits.

Lack of Evidence for Laboratory and Natural Vertical Transmission of Bluetongue Virus in Culicoides sonorensis (Diptera: Ceratopogonidae)

Culicoides sonorensis (Wirth & Jones) is the principal North American vector of bluetongue virus (BTV). BTV infection of livestock is distinctly seasonal (late summer and fall) in temperate regions of the world such as California, which has led to speculation regarding vertical transmission of the virus within the midge vector as a potential mechanism for interseasonal maintenance ("overwintering") of the virus. To evaluate potential vertical transmission of BTV in its midge vector, we fed adult midges BTV-spiked blood and used a BTV-specific quantitative reverse transcriptase polymerase chain reaction assay to evaluate parent, egg, and progeny stages of laboratory-reared C. sonorensis for the presence of viral nucleic acid. Whereas BTV nucleic acid was weakly detected in egg batches of virus-fed female midges, virus was never detected in subsequent progeny stages (larvae, pupae, and F1 generation adults). Similarly, BTV was not detected in pools of larvae collected from the waste-water lagoon of a BTV-endemic dairy farm in northern California during the seasonal period of virus transmission. Collectively, these results indicate that BTV is not readily transmitted vertically in C. sonorensis, and that persistence of the virus in long-lived parous female midges is a more likely mechanism for overwintering of BTV in temperate regions.

Bionomics of temperate and tropical Culicoides midges: knowledge gaps and consequences for transmission of Culicoides-borne viruses

Culicoides midges are abundant hematophagous flies that vector arboviruses of veterinary and medical importance. Dramatic changes in the epidemiology of Culicoides-borne arboviruses have occurred since 1998, including the emergence of exotic viruses in northern temperate regions, increases in global disease incidence, and enhanced virus diversity in tropical zones. Drivers may include changes in climate, land use, trade, and animal husbandry. New Culicoides species and new wild reservoir hosts have been implicated in transmission, highlighting the dynamic nature of pathogen-vector-host interactions. Focusing on potential vector species worldwide and key elements of vectorial capacity, we review the sensitivity of Culicoides life cycles to abiotic and biotic factors. We consider implications for designing control measures and understanding impacts of environmental change in different ecological contexts. Critical geographical, biological, and taxonomic knowledge gaps are prioritized. Recent developments in genomics and mathematical modeling may enhance ecological understanding of these complex arbovirus systems.

Estimating Culicoides sonorensis biting midge abundance using digital image analysis

ImageJ is an open-source software tool used for a variety of scientific objectives including cell counting, shape analysis and image correction. This technology has previously been used to estimate mosquito abundance in surveillance efforts. However, the utility of this application for estimating abundance or parity in the surveillance of Culicoides spp. (Diptera: Ceratopogonidae) has not yet been tested. Culicoides sonorensis (Wirth and Jones), a biting midge often measuring 2.0-2.5 mm in length, is an economically important vector of ruminant arboviruses in California. Current surveillance methods use visual sorting for the characteristics of midges and are very time-intensive for large studies. This project tested the utility of ImageJ as a tool to assist in gross trap enumeration as well as in parity analysis of C. sonorensis in comparison with traditional visual methods of enumeration using a dissecting microscope. Results confirmed that automated counting of midges is a reliable means of approximating midge numbers under certain conditions. Further evaluation confirmed accurate and time-efficient parity analysis in comparison with hand sorting. The ImageJ software shows promise as a tool that can assist and expedite C. sonorensis surveillance. Further, these methods may be useful in other insect surveillance activities.

Desiccation Tolerance in the Eggs of the Primary North American Bluetongue Virus Vector, Culicoides sonorensis (Diptera: Ceratopogonidae), and Implications for Vector Persistence

Culicoides sonorensis Wirth and Jones transmits bluetongue virus and develops in a variety of polluted mud habitats. Egg desiccation tolerance was tested by obtaining eggs of known age, drying them, and placing them back on wet substrate. Eggs 4-10 h old failed to hatch after 12 h of drying at 75% relative humidity (RH). Older eggs (28-34 h) survived severe desiccation and >50% water weight loss. They regained their water within ≈2 h of rehydration. Relative to control eggs, average egg hatch was reduced by 36% after 12 h of drying, 79% after 24 h, 91% after 36 h, and 97% after 48 h. Some embryos (1%) survived and hatched after 60 h of drying and water losses of nearly 60%. Eggs in specific 25-40 h age categories did not differ in hatch after a 12-h desiccation stress; critical embryo age to survive drying is between 10 and 24 h. Humidity gradients relieved desiccation stress, and eggs appeared to regain water from saturated RH conditions. Individual, gravid C. sonorensis oviposited in 1-liter containers with an artificial mud bank. If they laid eggs, 73% deposited them singly in lines ranging up to 5-6 cm in length (meanderers), while 27% laid eggs in clumps (dumpers). Eggs were positioned an average of 45 ± 12 mm back from waterline. Younger eggs, if laid in early evening, may not experience severe desiccation. Embryo recovery from such severe desiccation could be adaptive in ephemeral habitats where the species may have evolved.

Temperature governs on-host distribution of the northern fowl mite, Ornithonyssus sylviarum (Acari: Macronyssidae)

The northern fowl mite, Ornithonyssus sylviarum (Canestri & Fanzago), is an ectoparasite of more than 70 species of North American wild birds, but it has a particularly significant impact on chickens, where it is a permanent resident of vent feathers. Improved control practices depend on a better understanding of host-mite relationships. ISA Brown hens were inoculated experimentally with northern fowl mite adults, and northern fowl mite populations developed naturally. Using a fast-response microprobe, temperatures of individual vent feathers (n = 15) were recorded at 5-mm increments along the length of the feather shaft. Immediately after temperatures were recorded, the individual feathers were quickly clipped at the skin surface and then flash-frozen between 2 small blocks of dry ice, freezing all northern fowl mite stages in situ. The feathers then were cut into 5-mm sections for careful mite enumeration by life stage. There were no overall differences among life stages in the distributions on the feather. Mite positions on feathers (distance from skin) varied distinctly with feather zone temperatures, as well as with ambient and average temperatures over the prior 24 hr. Ambient temperature at time of sampling affected the positions of the 2 mobile categories, adults and larvae/nymphs, but showed no statistical relationship with egg distribution. In contrast, ambient 24-hr temperature influenced the positions of all life stages. On-host feather temperatures reflected ambient temperatures. Feathers collected on hot days (ambient temperatures of 23-33 C) provided a narrow and quite warm range of temperature conditions for mites (often >30-36 C). Temperatures on cool days (ambient temperatures of <23 C) provided much wider on-host temperature ranges for mites to occupy (13-35 C). Mites were farther from the skin on warmer days. When mites had a broad range of temperatures, the feather temperature zone occupied by all life stages averaged 28-29 C. Mites move to occupy favorable temperature conditions on-host. When further out on feathers in warm weather, and under thermal stress, northern fowl mites either move off host or are dislodged. They then become a human pest, are noticed by farmers, and are more likely to disperse.

Seasonal and interseasonal dynamics of bluetongue virus infection of dairy cattle and Culicoides sonorensis midges in northern California--implications for virus overwintering in temperate zones

Bluetongue virus (BTV) is the cause of an economically important arboviral disease of domestic and wild ruminants. The occurrence of BTV infection of livestock is distinctly seasonal in temperate regions of the world, thus we determined the dynamics of BTV infection (using BTV-specific real time reverse transcriptase polymerase chain reaction) among sentinel cattle and vector Culicoides sonorensis (C. sonorensis) midges on a dairy farm in northern California throughout both the seasonal and interseasonal (overwintering) periods of BTV activity from August 2012 until March 2014. The data confirmed widespread infection of both sentinel cattle and vector midges during the August-November period of seasonal BTV transmission, however BTV infection of parous female midges captured in traps set during daylight hours also was detected in February of both 2013 and 2014, during the interseasonal period. The finding of BTV-infected vector midges during mid-winter suggests that BTV may overwinter in northern California by infection of long-lived female C. sonorensis midges that were infected during the prior seasonal period of virus transmission, and reemerged sporadically during the overwintering period; however the data do not definitively preclude other potential mechanisms of BTV overwintering that are also discussed.

Seasonal variation and impact of waste-water lagoons as larval habitat on the population dynamics of Culicoides sonorensis (Diptera:Ceratpogonidae) at two dairy farms in northern California

The Sacramento (northern Central) Valley of California (CA) has a hot Mediterranean climate and a diverse ecological landscape that is impacted extensively by human activities, which include the intensive farming of crops and livestock. Waste-water ponds, marshes, and irrigated fields associated with these agricultural activities provide abundant larval habitats for C. sonorensis midges, in addition to those sites that exist in the natural environment. Within this region, C. sonorensis is an important vector of bluetongue (BTV) and related viruses that adversely affect the international trade and movement of livestock, the economics of livestock production, and animal welfare. To characterize the seasonal dynamics of immature and adult C. sonorensis populations, abundance was monitored intensively on two dairy farms in the Sacramento Valley from August 2012- to July 2013. Adults were sampled every two weeks for 52 weeks by trapping (CDC style traps without light and baited with dry-ice) along N-S and E-W transects on each farm. One farm had large operational waste-water lagoons, whereas the lagoon on the other farm was drained and remained dry during the study. Spring emergence and seasonal abundance of adult C. sonorensis on both farms coincided with rising vernal temperature. Paradoxically, the abundance of midges on the farm without a functioning waste-water lagoon was increased as compared to abundance on the farm with a waste-water lagoon system, indicating that this infrastructure may not serve as the sole, or even the primary larval habitat. Adult midges disappeared from both farms from late November until May; however, low numbers of parous female midges were detected in traps set during daylight in the inter-seasonal winter period. This latter finding is especially critical as it provides a potential mechanism for the "overwintering" of BTV in temperate regions such as northern CA. Precise documentation of temporal changes in the annual abundance and dispersal of Culicoides midges is essential for the creation of models to predict BTV infection of livestock and to develop sound abatement strategies.

Musca autumnalis (Diptera: Muscidae) and the host-specific nematode Paraiotonchium autumnale (Tylenchida: Iotonchiidae) in southern California

Musca autumnalis DeGeer were collected in the summer and fall of 2011 and 2012 from a beef cattle herd in southern California Visual counts of Musca spp. on cattle faces were documented, and sweep net samples of face flies and other Diptera were also collected from cattle faces. Face flies dominated in the net collections, and 5-30 flies per face were common between early July and October 2011. Adult female M. autumnalis were dissected and examined for the presence of the host-specific nematode Paraiotonchium autumnale (Nickle). Overall, 67 of 887 (7.6%) adult face fly females were parasitized. M. autumnalis' ability to survive in such a southerly latitude (34 degree N) could reflect the rather temperate weather (coastal effects) and frequently irrigated pastures at the experimental site in southern California Preliminary observations suggest that face flies disappear from cattle during winter, despite generally favorable temperatures for fly activity. This is a possible indication of diapause and should be examined further.

Gonotrophic development and survival in field populations of Musca domestica (Diptera: Muscidae) at dairies in California, Minnesota, and Georgia, and the relationship of fly age to relative abundance of (Z)-9-tricosene (muscalure)

Adult female Musca domestica L. were collected in 2004 and 2005 from dairies in California, Minnesota, and Georgia. Relative abundance of (Z)-9-tricosene (muscalure) among the dominant eight hydrocarbons was determined. Fly heads then were removed to quantify pterin levels and estimate fly age, abdomens were dissected to score gonotrophic development and parity (follicular relics), and spermathecae were examined for sperm. Daily survival was assessed using two estimates of time required to become gravid: laboratory-based degree-day (DD) estimates and estimates based on pterin values in field-collected flies matched to their stages of gonotrophic development. Among newly emerged females (oocyte stage 1) with detectable muscalure, it comprised < approximately 1.5% of cuticular hydrocarbons. In muscalure-positive flies, muscalure comprised a higher proportion of cuticular hydrocarbons in older flies from California and Minnesota (6-9% when gravid) versus flies from Georgia (<2% when gravid). Females mated in early-intermediate stages of egg development. Life expectancy, using laboratory-derived estimates of time needed to become gravid, ranged from 3.6 to 10.6 d. Using equivalent pterin-based time estimates, life expectancy ranged from 4.0 to 19.5 d. Mean DD ages (12 degrees C threshold) of gravid flies varied widely (53-95 DD) and were congruent with laboratory-based estimates (52-57 DD) in only 7 of 12 farm-year combinations. Thus, house flies under natural conditions often required more time to develop eggs than laboratory models would predict, extending daily survival estimates based on gonotrophic age by 11-74%.

A survey of Culicoides developmental sites on a farm in northern Spain, with a brief review of immature habitats of European species

Culicoides species (Diptera: Ceratopogonidae) belonging to the Obsoletus and Pulicaris groups are considered to be the main vectors of bluetongue virus (BTV) in non Mediterranean Europe. Selected terrestrial microhabitats (n=17) on a farm in northern Spain were sampled repeatedly over a year-long period and characterized for use by Culicoides species for immature development. Concurrent use of CDC light traps showed the presence of 37 species and 66,575 specimens of adult Culicoides. A total of 28 species and 11,396 individuals emerged from laboratory-maintained soil samples. Culicoides obsoletus and Culicoides scoticus (pooled as Obsoletus complex) were particularly abundant (comprising 58.6% and 74.5% of the total collections in light traps and emergence traps respectively). Potential key vectors of animal viruses (such as BTV) were found in two main terrestrial types of microhabitats. In the case of C. obsoletus, different types of manure (old and composted manure, manure mixed with organic matter, and fresh manure) produced most of the specimens. In contrast, larvae of C. scoticus and Culicoides lupicaris were associated with soil substantially comprised of rotting leaf litter that included the parasitic plant Lathraea clandestina. Several species, Culicoides festivipennis, Culicoides punctatus and Culicoides brunnicans, were very common in mud at pond margins. Indeed, pond microhabitats and runoff below barn rooflines supported the greatest species richness. In the pond habitat, 49.4% of Culicoides specimens emerged from mud at the water edge, as opposed to 50 cm above (32.4%) and 1 meter above waterline (18%). Similar species richness, but statistically significant differences in abundance, were observed among the four pond microhabitats. Overall, the majority of the specimens were found in the upper layer (0-3 cm), except in manure, where they preferred deeper layers (>6 cm). Maximum peaks of abundance occurred in both light traps and soil samples in summer months, whereas increased captures in autumn were noticed only in light traps. Both trapping systems failed to collect adult Culicoides midges in the coldest months of December, January and February. The literature on immature habitats of species suspected in BTV transmission in Europe, the Pulicaris group and particularly the Obsoletus group, is briefly reviewed.

Housing and dustbathing effects on northern fowl mites (Ornithonyssus sylviarum) and chicken body lice (Menacanthus stramineus) on hens

Hen housing (cage or cage-free) did not impact overall abundances of northern fowl mites, Ornithonyssus sylviarum (Canestrini & Fanzago) (Acari: Macronyssidae), or chicken body lice, Menacanthus stramineus (Nitzsch) (Phthiraptera: Menoponidae). Cage-free hens received a dustbox with sand plus diatomaceous earth (DE), kaolin clay or sulphur. Weekly use varied from none to 100% of hens; 73% of hens used the dustbox at least once. Ectoparasite populations on dustbathing hens (users) were compared with those on non-user cage-free and caged hens. All materials reduced ectoparasites on user hens by 80-100% after 1 week of dustbox use. Diatomaceous earth and kaolin failed to reduce ectoparasites on non-user hens, and ectoparasites on user hens recovered after dustbox removal. A sulphur dustbox eliminated mites from all hens (including non-users) within 2-4 weeks. Residual sulphur controlled mites until the end of the experiment (up to 9 weeks), even after the dustbox was removed. Louse populations on hens using the sulphur dustbox were reduced in 1-2 weeks. Residual sulphur effects were less evident in lice, but the use of a sulphur dustbox by a higher proportion of hens extended louse control to all hens. This is the first experimental study to show that bird dustbathing in naturally and widely available dust materials (particularly kaolin) can suppress ectoparasites and thus the behaviour is probably adaptive.

Evaluation of ammonia, human sweat, and bovine blood as attractants for the female canyon fly, Fannia conspicua (Diptera: Muscidae), in southern California

Human sweat, liquid ammonia, and bovine blood are known to be attractive to some hematophagous flies. These materials were evaluated with and without carbon dioxide (CO(2)) for their ability to increase capture of female "canyon flies" (Fannia conspicua Malloch) using CDC-type suction traps (without light). Ammonia acted synergistically with CO(2) to increase trap catch 89.9% over CO(2) alone. There was no synergistic effect of human sweat or bovine blood with CO(2). In the absence of CO(2), none of the three materials increased trap catch of female canyon flies relative to non-baited traps. Implications for canyon fly control and further trap improvement are discussed.

Hen welfare in different housing systems

Egg production systems have become subject to heightened levels of scrutiny. Multiple factors such as disease, skeletal and foot health, pest and parasite load, behavior, stress, affective states, nutrition, and genetics influence the level of welfare hens experience. Although the need to evaluate the influence of these factors on welfare is recognized, research is still in the early stages. We compared conventional cages, furnished cages, noncage systems, and outdoor systems. Specific attributes of each system are shown to affect welfare, and systems that have similar attributes are affected similarly. For instance, environments in which hens are exposed to litter and soil, such as noncage and outdoor systems, provide a greater opportunity for disease and parasites. The more complex the environment, the more difficult it is to clean, and the larger the group size, the more easily disease and parasites are able to spread. Environments such as conventional cages, which limit movement, can lead to osteoporosis, but environments that have increased complexity, such as noncage systems, expose hens to an increased incidence of bone fractures. More space allows for hens to perform a greater repertoire of behaviors, although some deleterious behaviors such as cannibalism and piling, which results in smothering, can occur in large groups. Less is understood about the stress that each system imposes on the hen, but it appears that each system has its unique challenges. Selective breeding for desired traits such as improved bone strength and decreased feather pecking and cannibalism may help to improve welfare. It appears that no single housing system is ideal from a hen welfare perspective. Although environmental complexity increases behavioral opportunities, it also introduces difficulties in terms of disease and pest control. In addition, environmental complexity can create opportunities for the hens to express behaviors that may be detrimental to their welfare. As a result, any attempt to evaluate the sustainability of a switch to an alternative housing system requires careful consideration of the merits and shortcomings of each housing system.

Diel patterns of female host seeking, male swarming, and sugar feeding in Fannia conspicua (Diptera: Muscidae) in southern California

Adult Fannia conspicua Malloch were captured by sweep net at a southern California coastal mountain community to determine diel flight activity and crop/gut sugar (gut sugar) concentration. Male swarming activity was monitored by visual estimation of swarm numbers. Gut sugar content of captured flies was determined by cold anthrone assay. Peak host seeking by female flies generally occurred in early morning (0700-0800) and early evening (1900-2000). Variation in female host-seeking activity was significantly explained by the time elapsed since sunrise or time remaining until sunset, with temperature, humidity, and wind speed having small, but significant effects on activity. Male swarming activity occurred more generally throughout the day, with peaks in mid-morning and mid-afternoon and reduced swarming during periods of highest female host-seeking activity. Male swarming behaviors were only minimally explained by environmental variables. Flies of both sexes commonly fed on fructose sugars with 99.94% of host-seeking female flies (n = 1,647), and 98.93% of swarming male flies (n = 1,398) with gut sugar levels exceeding those of starved flies. Host-seeking female flies had significantly higher overall sugar content than swarming male flies. Male flies had peak gut sugar levels at 0800-0900 and 2000. Female flies had broad peaks in gut sugar level from 0700 to 1200 and 1600 to 1900. Stepwise regression showed that variation in gut sugar level was poorly explained by environmental variables for both sexes.

Responses of Ornithonyssus sylviarum (Acari: Macronyssidae) and Menacanthus stramineus (Phthiraptera: Menoponidae) to gradients of temperature, light, and humidity, with comments on microhabitat selection on chickens

Responses of the northern fowl mite (NFM), Ornithonyssus sylviarum (Canestrini & Fanzago) (Acari: Macronyssidae), and the chicken body louse (CBL), Menacanthus stramineus (Nitzsch) (Phthiraptera: Menoponidae), to variation in temperature, light, and humidity were assessed in bioassays. The location on a continuous thermal gradient at which each ectoparasite arrested was recorded and analyzed. NFM adults arrested at an average temperature of 30.09 +/- 0.34 degrees C. Adult CBL and first-instar CBL nymphs arrested at 33.69 +/- 0.20 degrees C and 34.99 +/- 0.26 degrees C, respectively. Groups of each ectoparasite were placed into clear glass vials (n = 10/vial) with one half shaded, and vials were exposed to three light levels, as follows: high (200 micromolm(-2)s(-1)), low (4 micromolm(-2)s(-1)), and nearly no light (0 micromolm(-2)s(-1)). The vial cap edges provided an opportunity to assess the interactive effect of light with harborage. NFM avoided light and sought harborage. In low light, the harborage preference overrode the tendency to avoid light. CBL avoided the harborage and showed a minimal preference for light. A four-level humidity gradient was established in two separate experimental arenas for NFM and CBL. Trials were run in ambient light (4 micromolm(-2)s(-1)) for the NFM and in nearly no light for the CBL. The NFM gradient used 38 +/- 2%, 54 +/- 7%, 73 +/- 3%, and 90 +/- 4% RH, whereas the CBL gradient used 42 +/- 5%, 48 +/- 7%, 63 +/- 4%, and 73 +/- 5% RH. NFM showed no humidity response in the walking bioassay, but the CBL settled at the lowest humidity level. Temperature and humidity on different hen body regions were related to the bioassay results and observed on-host ectoparasite distributions.

Beak condition and cage density determine abundance and spatial distribution of northern fowl mites, Ornithonyssus sylviarum, and chicken body lice, Menacanthus stramineus, on caged laying hens

Adult White Leghorn hens (Hy-Line strain W-36) were inoculated with either northern fowl mites or chicken body lice, and the ectoparasite populations were monitored over periods of 9 to 16 wk. Two beak conditions (beak trimmed or beak intact) and 2 housing densities (1 or 2 hens per 25 × 31 cm suspended wire cage) were tested. Populations of both ectoparasites were at least 10 times lower on beak-intact hens compared with populations on beak-trimmed hens. Cage density did not influence mite numbers, but higher numbers of lice (2 to 3 times) developed on hens held at the higher cage density. Louse distribution on the body and louse population age structure were also influenced by host beak condition. Beak-intact hens had a higher proportion of lice under the wings, whereas beak-trimmed hens had the majority of lice on the lower abdomen. Louse populations on beak-trimmed hens also comprised relatively more immature stages than populations found on beak-intact hens. The effects are likely related to decreased grooming efficiency by beak-trimmed hens and, in the case of lice, the higher host density. The high mite and louse populations on most commercial caged laying hens are probably a direct result of beak trimming. However, selection of more docile breeds that can be held without trimming may allow the hens themselves to reduce ectoparasites below economically damaging levels. This could benefit producers, animal welfare advocates, and human health by reducing 1) costs of beak trimming, 2) pesticide treatment costs (including human and bird chemical exposure concerns), and 3) objections to beak trimming from the animal welfare community.

Adult house fly (Diptera: Muscidae) activity and age of females near varying levels of (Z)-9-tricosene on a southern California dairy

The number of adult male and female house flies, Musca domestica L. (Diptera: Muscidae), near varying levels of (Z)-9-tricosene alone (5, 50, or 100 micdrol) or combined (50 microl) with sugar was determined using conical screened traps on a dairy in southern California. Overall, significantly more males than females were collected in the traps. Significantly more flies (male and female) were collected in traps with (Z)-9-tricosene. There were no significant differences among doses of (Z)-9-tricosene alone, but numbers of both sexes were significantly higher in traps baited with (Z)-9-tricosene and sugar compared with the 5- and 50-microl doses without sugar. The age of female flies collected in traps was determined by pterin analysis. Mean female ages ranged from 94.7 to 99.6 degree-days (6.3-6.8 d of age) and did not differ significantly among treatments. Dissections of a subset of females from each treatment determined that collected females were primarily nongravid (86.3%). Proportions of gravid females that were collected did not differ among treatments.