Impaired discrimination of and aversion to parasitized male odors by female oxytocin knockout mice

A major cost of social behavior is the increased risk of exposure to parasites, with animals utilizing social information to recognize and avoid infected conspecifics. In mice, females can discriminate between infected and uninfected males on the basis of social cues, displaying aversive responses to the odors of infected males. In the present study, using female mice whose gene for oxytocin (OT) has been selectively deleted (OT knockout mice (OTKO)), we show that at least one normal allele for OT is required for the mediation of the recognition and avoidance of parasitized males. Female wild type (OTWT) and heterozygous (OTHZ) mice distinguished between the odors of individual males infected with the louse, Polyplax serrata, and uninfected males while the KO mice did not. Exposure to the odors of infected males induced analgesia in OTWT and OTHZ females, with OTKO females displaying attenuated analgesia. OTWT and OTHZ females, but not the OTKO females, also distinguished between the odors of novel and familiar infected males and modulated their analgesic responses on the basis of prior familiarity. In an odor choice test, OTWT and OTHZ females displayed a marked initial choice for the odors of uninfected males, whereas the OTKO females showed no consistent choice. This impairment was specific to the odors of infected males. OTKO females displayed normal analgesic responses to another aversive social odor, that of a stressed male, and an aversive non-social odor, that of a cat. The OTKOs had normal non-social olfactory memory, but were impaired in their social odor memory. These findings indicate that a normal OT gene comprises an essential part of the central recognition mechanism whereby females can both reduce the transmission of parasites to themselves and select for parasite-free males.

Prevalence of sucking and chewing lice on cattle entering feedlots in southern Alberta

Beef calves from 2 sources entering southern Alberta feedlots in the winters of 1997-98 and 1998-99, were surveyed for the presence of lice. A random sample of multiple source (MS), that is, auction market-derived, calves entering commercial feedlots and single source (SS) calves entering a backgrounding feedlot were examined for the presence of lice at entry to the feedlot. A standardized examination, which involved hair-part examination of 8 louse predilection sites, was conducted on each selected calf to determine prevalence and intensity of infestation. The long-nosed sucking louse, Linognathus vituli, was the most commonly encountered species. This species infested from 57.8% to 95.6% of the calves selected from both MS and SS calves during both winters. Louse index values, indicating intensity of infestation, for L. vituli ranged from 1 to 243 lice per animal. The chewing louse, Bovicola bovis, was present on MS and SS calves only in the winter of 1998-99. The louse index values for B. bovis ranged from 1 to 230 lice per animal. Mixed infestations of the L. vituli and B. bovis were common. The little blue cattle louse, Solenopotes capillatus, was present only on the SS calves in the winter of 1997-98. The short-nosed sucking louse, Haematopinus eurysternus, was present at very low intensities, 1-2 lice per animal, on 2.6% to 4.4% of the MS calves during both winters. Comparison of results from the current study with published literature suggests that efforts to determine the economic impact of louse infestations are confounded by the lack of a uniform method to assess louse population levels.

Keratoconjunctivitis and periorbital papillomatosis associated with heavy periorbital infestation by the tail louse Haematopinus quadripertusus in heifers

Heifers (Israeli-Holstein), aged 12-18 months, permanently maintained in open barns on an inadequate nutritional regime were found to be moderately to heavily infested by Haematopinus quadripertusus, the tail louse. The severely infested heifers showed keratoconjunctivitis and periorbital papillomatosis. Two treatments with an alpha-cypermethrin pour-on product 14 days apart controlled the lice, and were followed by alleviation of the inflammation and regression of the papillomas.

Eradication of lice in cattle

The purpose of this field study was to develop and evaluate eradication as a strategy to control lice in cattle. Thirty-three herds of cattle were selected and observed during a period of two and a half years. Before eradication, biting lice (Damalinia bovis) were present in 94% of the herds and 27% of the animals. Sucking lice (Linognathus vituli) were present in 42% of the herds and 5% of the animals. These levels were very similar to those reported from other countries in Northern Europe. The eradication strategy was successful in 28 of 33 herds, but lice were still present in 5 herds 3 to 6 months after treatment. Biting lice were present in all these 5 herds, sucking lice were present in 3 herds. During the next 12 months, nine of the 28 herds were reinfected with lice. Six herds were reinfected with just biting lice, 2 herds with just sucking lice and one herd was reinfected with both. There was no significant difference between the 2 louse species regarding the risk of unsuccessful eradication or reinfection. The only significant risk factor for reinfection was either purchase of livestock or use of common pasture, combined with failure in pre-treatment of newly introduced animals.

[The influence of skin parasite infection on the productivity of gilts at pig testing stations]

On the basis of skin scrapings collected together with cerumen from the inside of ears, the occurrence of a hidden mite and louse infection was assessed to evaluate its effect on the productive traits of gilts fattened during 1996-1997 at Pig Testing Stations (PTS). The productivity was highly influenced by the station factors. The low level of infection had, however, some negative effect in a few cases, and in few it was not clear, probably due to the phenomenon of resilience.

[The importance of different pig diseases in the Netherlands]

As part of the project 'Clean pigs', IPG Institute for Pig Genetics BV made an inventory of the impact of different diseases on the Dutch pig industry. An expert panel assessed the importance of the different diseases with regard to public health, farm economy, the pig sector and export sales. The possibilities for the diagnosis of the different pathogens were listed and the goal for the next years, was set. Diseases were classified into three categories, according to their importance for the Dutch pig industry (Table 2). The diseases that can be eradicated are Salmonella (only specific strains), Pasteurella multocida DNT + PAR), Actinobacillus pleuropneumoniae, Haematopinus suis (lice) and Sarcoptes scabei (var. suis) (mange). National introduction of list A en most list B diseases of the OIE classification must be prevented.

Efficacy of a pour-on formulation of doramectin against lice, mites, and grubs of cattle

OBJECTIVE

To determine effectiveness of a pour-on formulation of doramectin against Damalinia bovis, Haematopinus eurysternus, Linognathus vituli, Solenopotes capillatus, Chorioptes bovis, Sarcoptes scabiei, Hypoderma bovis, and Hypoderma lineatum.

ANIMALS

Cattle of various ages with naturally acquired or artificial infestations with 1 or more species of lice, mites, or grubs.

PROCEDURE

In 10 louse and 6 mite studies, cattle were treated with doramectin (500 microg/kg, topically) on day 0, and parasite counts were performed approximately weekly from days 0 to 35. In 6 grub studies, cattle expected to harbor Hypoderma spp were treated before emergence of warbles. After warbles began to emerge, they were counted every 2 weeks, and grubs were collected and identified by species.

RESULTS

Burdens of D bovis, H eurystemus, L vituli, and S capillatus on doramectin-treated cattle were 0 by 28 days after treatment. Burdens of C bovis and S scabiei decreased to 0 in naturally infested cattle and approximately 0 in artificially infested cattle by day 14 to 15. In grub studies, 107 of 136 control cattle had warbles, whereas 2 of 136 doramectin-treated cattle had 1 warble each, which represented a cure rate of 98.5%.

CONCLUSION AND CLINICAL RELEVANCE

One topical application of doramectin was highly efficacious against common species of lice, mites, and grubs known to affect performance, health, and appearance of cattle.

Eprinomectin: a novel avermectin for control of lice in all classes of cattle

Eight trials were conducted in the United States to determine the efficacy of eprinomectin applied topically against four common species of lice in cattle. In two dose titration trials, eprinomectin dosages of 125 to 750 mcg/kg body weight applied topically were compared to untreated controls. In dose confirmation studies, animals treated topically with eprinomectin applied at the rate of 500 mcg/kg were compared to vehicle-treated controls. Four species of lice were present in these trials: Linognathus vituli, Haematopinus eurysternus, Solenopotes capillatus, all sucking lice, and Damalinia (Bovicola) bovis, the cattle biting louse. Louse counts were made on six to nine predilection sites (the same number of sites in all animals in the same trial) prior to treatment. The same sites were counted again seven days after treatment and weekly thereafter until trial termination eight weeks after treatment. When no lice were found in the predilection sites, a modified whole body search was conducted. Each species of lice was present on at least six animals in each treatment group on at least one counting date in two or more trials. No lice were found on any animal treated topically with eprinomectin at a dosage of > or = 500 mcg/kg after 14 days posttreatment until termination of the trials eight weeks after treatment.

Doramectin systemic activity against cattle grubs, Hypoderma lineatum and H. bovis (Diptera: Oestridae), and cattle lice, bovicola bovis (Mallophaga: Trichodectidae), Linognathus vituli and Solenopotes capillatus (Anoplura: Linognathidae), and Haematopinus eurysternus (Anoplura: Haematopinidae), in Wyoming

Seven individual trials were conducted in Wyoming to evaluate the therapeutic efficacy of doramectin administered subcutaneously at a dosage of 200 micrograms kg-1 against multiple, natural infestations of cattle grubs or cattle lice. Insect species present and the number of trials that included each species were: Hypoderma lineatum, 2; Hypoderma bovis. 1; Bovicola bovis, 5; Haematopinus eurysternus, 1; Linognathus vituli, 5; and Solenopotes capillatus, 3. Examinations for lice were performed prior to treatment and either weekly or bi-weekly thereafter for 28 days. Examinations for cattle warbles were performed either weekly or every 4 to 5 weeks from time of first appearance through last appearance in the backs of the cattle. No H. lineatum, H. bovis, H. eurysternus, L. vituli, or S. capillatus were found on doramectin-treated animals at any time following treatment. By 28 days following treatment, the number of B. bovis was reduced between 58 and 98%. Treatments applied later in the season, i.e. in March, were more efficacious against B. bovis than those applied in January or February.

Effects of the sucking louse (Linognathus vituli) on the grooming behaviour of housed calves

The behaviour of cattle with and without louse infestation was studied for eight weeks. Thirty-two crossbred calves were housed in groups of four at 20 weeks old. Sixteen of the calves were artificially infested with the long-nosed cattle louse Linognathus vituli and 16 were left uninfested as controls. In infested animals the number of lice on the shoulders averaged 2.3 per 10 cm length of parted hair. The recorded frequency of irritation, manifested by rubbing and self-licking, was significantly greater in the louse-infested calves than in the uninfested controls. The infested calves spent 28 s/h rubbing and 95 s/h self-licking, compared with 8 s and 62 s/h spent by the uninfested controls. The infested calves also spent more than twice as long scratching as the controls. There were no significant effects of the infestation on social grooming.

Some ectoparasites of commensal rodents from Huambo, Angola

Eight species of ectoparasites were collected from 166 commensal rodents, including Rattus rattus (L.), Rattus norvegicus (Berkenhout), and Mus musculus (L.), from January to December 1986, in Huambo, Angola. The oriental rat flea, Xenopsylla cheopis (Rothschild), was the predominant species with respect to mean intensity and prevalence. Other fleas collected were Ctenophthalmus (Ethioctenophthalmus) machadoi Ribeiro, Dinopsyllus (Dinopsyllus) smiti Ribeiro, and Echidnophaga gallinacea (Westwood). The mite Laelaps (Echinolaelaps) muricola Trägärdh, the louse Polyplax spinulosa (Burmeister), one species of Ixodes Latreille, and one species of Ornithonyssus Sambon were also recorded. The following represent new host records: C. machadoi from R. rattus and R. norvegicus, D. smiti from M. musculus, and L. muricola from R. rattus and M. musculus. For the first time, the monthly flea indices throughout the year are presented for Angola.

Spectrum of activity of doramectin against cattle mites and lice

A series of 16 studies was conducted involving 288 cattle with naturally acquired or experimentally induced mite or louse infestations to evaluate the efficacy of doramectin. Four studies were conducted against the mite species Psoroptes bovis and two against the mite species Sarcoptes scabiei. Ten studies involved cattle with one or more of the following louse species: Damalinia bovis, Haematopinus eurysternus, Linognathus vituli and Solenopotes capillatus. In each study, a group of at least nine but not more than 25 cattle were randomly allocated to a control or a treated group. One group was treated with doramectin at 200 micrograms kg-1 and the other group received no medication. Mites or lice were quantified by species immediately before treatment and at weekly intervals for 4 weeks thereafter. Doramectin was 100% efficacious against infestations of P. bovis, Sarcoptes scabiei, H. eurysternus, L. vituli and Solenopotes capillatus. The drug reduced infestations of D. bovis by a mean of 82%.

The efficacy of injectable and pour-on formulations of moxidectin against lice on cattle

The efficacy of one administration of moxidectin against natural infestations of the 3 common species of cattle lice in Australia: Linognathus vituli, Damalinia bovis and Haematopinus eurysternus, was determined. A high degree of control of L vituli (the long-nosed sucking louse) was achieved with both the cattle injection (96.7% and 100%) at 0.2 mg/kg and the cattle pour-on formulation (94.6% and 100%) at 0.5 mg/kg on the 2 farms where this louse occurred. An injection of moxidectin at 0.2 mg/kg did not eliminate D bovis. In these trials efficacy ranged from nil to 85.2%. In contrast the pour-on formulation at 0.5 mg/kg provided consistently high efficacy (83.6 to 100%) against D bovis on 3 farms. Infestations of H eurysternus (the short-nosed sucking louse) were low and no significant difference was recorded between treatment groups in a single trial, however, lice persisted on 3 to 7 cattle in the untreated group at each inspection, whereas none were found on any animals in the 2 groups treated with moxidectin on inspection after treatment.

Parasitic arthropods of sympatric opossums, cotton rats, and cotton mice from Merritt Island, Florida

Six species of parasitic arthropods were collected from 12 opossums (Didelphis virginiana), 8 species were obtained from 28 cotton rats (Sigmodon hispidus), and 4 species were collected from 10 cotton mice (Peromyscus gossypinus) from Merritt Island, Brevard County, Florida. The flea Polygenis gwyni was the only parasite that infested all 3 host species, and it was present in very high densities (mean intensity = 73.7) on the opossums. The American dog tick, Dermacentor variabilis, and the tropical rat mite, Ornithonyssus bacoti, both infested 2 host species but were principally associated with opossums and cotton rats, respectively. All remaining arthropod species were confined to single host species, suggesting host specificity by these parasites. The atopomelid mite Didelphilichus serrifer and the myobiid mite Radfordia sigmodontis constitute new state records for Florida. The reptile tick Amblyomma dissimile is recorded from a cotton mouse for the first time; Merritt Island may represent the most northerly location for viable populations of this tick in the U.S.A.

Ectoparasites from elk (Cervus elaphus nelsoni) from Wyoming

Hides of nine elk, collected during the winter of 1986-1987 from the National Elk Refuge, Wyoming (USA) were examined for ectoparasites. Parasites recovered were mites, Psoroptes sp. (five elk); lice, Solenopotes ferrisi and Bovicola (Bovicola) longicornis (seven elk); and winter ticks, Dermacentor albipictus (nine elk). Three elk with severe scabies had an estimated 0.6 x 10(6), 3.8 x 10(6) and 6.5 x 10(6) mites, respectively. Densities of mites were much higher in skin regions with severe dermatitis. Skin lesions on elk with scabies consisted of dense, often moist, scabs extending along the dorsal and lateral thoracic regions of the body. Lesions attributed to winter ticks consisted of broken hair and alopecia on the dorsal portion of the lower neck, often extending in a "collar" around the neck.

The ocular manifestations of sexually transmitted diseases

The problem of ocular involvement in sexually transmitted diseases is encountered by ophthalmologists in everyday practice. This paper reviews the ocular manifestations of some of the more common sexually transmitted diseases including AIDS, syphilis, gonorrhea and infections caused by herpes simplex, Chlamydia trachomatis and Phthirus pubis. Current methods of diagnosis and treatment are discussed. Neonatal infections associated with sexually transmitted diseases are also reviewed.

Ectoparasites of black-tailed prairie dogs (Cynomys ludovicianus) from South Dakota

During the summers of 1982 and 1983, black-tailed prairie dogs (Cynomys ludovicianus) were examined for parasites. Those collected and their respective prevalence included Linognathoides cynomyis (46.3%), Opisocrostis hirsutus (53.7%), Opisocrostis tuberculatus cynomuris (2.4%), Androlaelaps fahrenholzi (12.2%), Ixodes sculptus (2.4%) and Dermacentor andersoni (4.9%). The collection data indicated that L. cynomyis, O. hirsutus and A. fahrenholzi were at low population densities during this period.

Ectoparasitic fauna of poultry in Nsukka, Nigeria

An investigation which lasted for a period of one calendar year was mounted to determine common ectoparasitic fauna of poultry in Nsukka, Nigeria. This survey covered twenty commercial poultry farms located in different areas of Nsukka. Birds were picked and thoroughly examined visually for the presence of ectoparasites after horizontal displacement of the feathers against their anatomical direction of alignment. Identification was mainly by morphological characteristics, host preference and anatomical location. The result of the survey indicates that 15 (75%) out of a total of 20 farms sampled were infested. Furthermore, the orders Mallophaga and Anoplura were commonly recovered. Common ectoparasites identified and their prevalence rates are as follows: Gonoides gigas (15.0%), Menacanthus stramineus (20.0%), Lipeurus caponis (25.0%), Ceratophyllus gallinae (25.0%) and Amblyomma sp. (15.0%). The veterinary importance of these ectoparasites are highlighted and possible control measures against ectoparasitic build up in poultry houses recommended.

Ectoparasitic infestation of the lashes

Phthirus pubis, commonly known as the crab louse, has as its habitat the pubic and inguinal regions of the body. Transfer between hosts is most commonly a result of sexual contact. On occasion, Phthirus pubis will leave its usual seat of predilection and infest other hair-bearing body parts. When infestation of the eyelashes occurs, it is known as phthiriasis palpebrarum. The case presented is an example of phthiriasis palpebrarum in a young female, apparently contracted as a result of transfer from the genital region of an affected male by hand contact.

[Ectoparasites in rodents of the urban region of Belo Horizonte, MG. III. Fleas, Anoplura and Acari indices in Rattus norvegicus norvegicus]

The total and specific indices of fleas, lice and mites were determined for ectoparasites on Rattus norvegicus norvegicus capture in urban areas of Belo Horizonte, Minas state, Brazil, from June 1980 to September 1982. In view of the limiting or critical values attributed to flea indices above all the "cheopis" index, proposed by several authors as a complementary measure for bubonic plague surveillance, the community of Belo Horizonte would have been exposed to this infection. The annual total indices ranged from 0.3 to 2.4 and the prevalent flea was Xenopsylla cheopis (99.2%), with the highest indices coinciding with the late dry-cool season. On two occasions, in this period, the community would have remained highly exposed to infection, since the index-limits were superseded: 8.8 (October 1980) and 6.2 (September 1982). It is suggested that preventive measures, such as protection against rat insecticide treatment may be efficiently applied in the late dry-cool season, or previous to the rainy season, before the elimination of rats. Reports on indices of lice and mites are important as they may establish index-limits for certain infections exclusive to rodents.