Distribution of Culicoides sonorensis (Diptera: Ceratopogonidae) in Nebraska, South Dakota, and North Dakota: clarifying the epidemiology of bluetongue disease in the northern Great Plains region of the United States

The presence or absence of the biting midge Culicoides sonorensis Wirth & Jones (Diptera: Ceratopogonidae), a primary vector of bluetongue viruses (genus Orbivirus, family Reoviridae, BTV) in North America, was assessed on ranches and farms across the Northern Great Plains region of the United States, specifically Nebraska, South Dakota, and North Dakota, as part of a 2-yr regional study of BTV exposure among cattle. Blacklight/suction trap samples totaling 280 2-night intervals were taken at 140 aquatic sites (potential larval habitat for C. sonorensis) on 82 livestock operations (ranches and farms) that span a south-to-north gradient of expected decreasing risk for exposure to BTV. In Nebraska, C. sonorensis populations were common and widespread, present at 15 of 18 operations. Of 32 operations sampled in South Dakota, seven of which were sampled in successive years, 18 were positive for C. sonorensis; 13 of 14 operations located west of the Missouri River were positive, whereas 13 of 18 operations east of the river were negative. Of 32 operations sampled in North Dakota, seven of which were sampled both years, 12 were positive for C. sonorensis. Six of eight operations located west and south of the Missouri River in North Dakota were positive, whereas 18 of 24 operations east and north of the river were negative for C. sonorensis. These data illustrate a well-defined pattern of C. sonorensis spatial distribution, with populations consistently present across Nebraska, western South Dakota, and western North Dakota; western South Dakota, and North Dakota encompass the Northwestern Plains Ecoregion where soils are nonglaciated and evaporation exceeds precipitation. In contrast, C. sonorensis populations were largely absent east of the Missouri River in South Dakota and North Dakota; this area comprises the Northwestern Glaciated Plains Ecoregion and Northern Glaciated Plains Ecoregion where surface soils reflect Wisconsinan glaciation and precipitation exceeds evaporation. In defining a well-demarcated pattern of population presence or absence on a regional scale, the data suggest that biogeographic factors regulate the distribution of C. sonorensis and in turn BTV exposure. These factors, ostensibly climate and soil type as they affect the suitability of larval habitat, may explain the absence of C. sonorensis, hence limited risk for exposure to BTV, across the eastern Northern Plains, upper Midwest, and possibly Northeast, regions of the United States.

Landscape associations of the sand fly, Lutzomyia (Heleocyrtomyia) apache (Diptera: Psychodidae), in the southwestern United States: a geographic information system analysis

Landscape associations of the sand fly, Lutzomyia apache, Young and Perkins, in the southwestern U.S. were investigated by light/suction trap sampling and the development of a GIS-generated distribution map. In the mid-Rio Grande River valley, N.M., female and male L. apache were captured in updraft light/suction traps set in desert shrubland, irrigation levee, and bosque vegetation communities. Small numbers of flies were captured, but the presence of males and females in spatially separate and diverse plant communities at two locations suggest that L. apache are dispersed among available vegetation types. These data, along with 22 previously published collection site records, were used with a suite of physiographic features to characterize the biogeographic conditions suitable for L. apache. Suitable conditions encompass three life zones: the Rocky Mountain steppe province, the Colorado semi-plateau province, and the American semi-desert province, all within the dry domain region of the western U.S. The potential range of L. apache was then estimated based on elevation, mean and max - min temperature, precipitation, wet days, and relative humidity. The estimated range includes large contiguous areas in north-central Colorado, east-central New Mexico and west Texas, the lower mid-Rio Grande River valley, and southern Arizona, along with smaller, patchy, areas in northern Arizona, California, Nevada, Utah, and central Idaho. The spatial relationship between the estimated distribution of L. apache and the location of livestock exposed to vesicular stomatitis virus at the onset of recent outbreaks is presented.

Sampling for sand flies (Diptera: Psychodidae) among prairie dog colonies on ranches with histories of vesicular stomatitis in new Mexico and Colorado

The possible presence of sand flies (Diptera: Psychodidae) among colonies of Gunnison's prairie dogs, Cynomys gunnisoni Baird, was investigated on or near ranches with histories of vesicular stomatitis (VS) in domestic livestock in the mid-Rio Grande River Valley, NM, and west-slope region of Colorado. Sampling was conducted at six locations, three in each region, using three methods: standard down-draft suction/light traps, up-draft suction/light traps (both supplemented with CO2), and burrow-emergence traps. Two male and four female sand flies, Lutzomyia apache, Young and Perkins were recovered from prairie dog colony and sand-sagebrush association habitats on a cattle ranch in Socorro County, NM. Sand flies were captured only in up-draft suction/light traps. This record is of interest for the following reasons: (1) sand flies have not been reported from the Rio Grande River Valley of New Mexico, (2) sand flies are biological vectors of VS viruses in other areas, (3) the mid-Rio Grande River Valley has been a focus of VS virus activity in domestic livestock during recent outbreaks, and (4) the source of vesicular stomatitis viruses that infect livestock in the western United States is unknown, but may involve introductions of virus from Mexico or an endemic cycle maintained by vector insects.

Longitudinal studies in the epidemiology of vesicular stomatitis on Costa Rican dairy farms

Twenty-three Costa Rican dairy herds from an vesicular stomatitis (VS) endemic area were under an active surveillance between April 1997 and March 1999. Ninety-two confirmed cases of VS New Jersey were found. Factors associated with clinical cases of VS virus New Jersey were: Parity (animals of parity 4 or 5 were 5.3 times more likely to present a clinical case than animals of parity 3 and lower; on the other hand, animals of parity 6 and higher showed an odds 4.6 times greater than animals of parity 3 and lower.) Ecological life zone (animals in premountain moist forest were 7.4 times more likely to present clinical cases than animals in lower mountain rain forest). Factors associated with seropositivity at the time of birth were farm and breed (Jersey calves had an odds 14.7 times greater than Holstein calves). Seroconversion, defined as the first twofold increase in the titers of the blood, was associated with farm and showed four peaks during the study period, September (wet season) 1997, February (dry season) 1998, September 1998, and February 1999. Finally, time to event analysis showed difference between farms and age, older animals showed the first seroconversion earlier than younger animals.

Survey of small rodents and hematophagous flies in three sentinel farms in a Costa Rican vesicular stomatitis endemic region

A survey of rodents and hematophagous flies was conducted on three farms located in an area endemic for vesicular stomatitis to determine the species composition of each zoological group occurring in these areas. Eleven species of small rodents were collected and identified. Individuals from forty-nine species of hematophagous flies of the families Ceratopogonidae, Culicidae, and Phlebotominae were captured and identified. The species compositions in each group were compared between farms. Rodents were tested for antibodies to vesicular stomatitis, New Jersey and Indiana serotypes. Seven species had antibody titers greater than 1:10. Attempts to isolate the virus produced negative results for all the species tested.

Temporal and spatial variation of phlebotomine (Diptera: Psychodidae) community diversity in a cutaneous leishmaniasis endemic area of Costa Rica

Phlebotomine sand fly species composition and diversity were studied in Acosta, an area of Costa Rica endemic for cutaneous leishmaniasis. Two CDC miniature light traps per house were set overnight in 72 houses distributed in 6 localities, once a month, during the rainy seasons of 1994 and 1995. Of the 22 species collected, the most common were Lutzomyia serrana (Damasceno & Arouck), L. youngi Feliciangelli & Murillo, L. ylephiletor (Fairchild & Hertig), L. shannoni (Dyar), L. cruciata (Coquillett), L. gomezi (Nitzulescu), L. sanguinaria (Fairchild & Hertig), and Warileya rotundipennis (Fairchild & Hertig). The Czekanowsky index and the Sorensen index as modified by Bray and Curtis to consider abundance were used to compare species composition and beta-diversity. Comparisons were made among localities within years, between years, and localities each year. The data strongly indicated that phlebotomine species composition is more stable than diversity or abundance.

Prospective study for the detection of Anaplasma marginale Theiler, 1911 (Rickettsiales: Anaplasmataceae) in Costa Rica

A prospective study was conducted to assess the dynamics of the infection and host response to Anaplasma marginale in one closed herd in the dry tropical forest of Costa Rica. The study subjects were the dams and their calves born during 1 breeding season (1995-1996). All cows were sampled at 3 month intervals for antibody detection using a competitive ELISA (cELISA) and for antigen detection using PCR/nonradioactive probe assay. All 24 calves born during the study were individually identified at birth and subsequently sampled each month for PCR and cELISA. Ticks were identified from all animals throughout the entire study period. The results from this study confirmed that the cELISA is a reliable assay for identifying new and carrier infections and that carrier infections can exist at levels below that detectable by PCR. In addition, it was demonstrated that calves born in this region will most likely be exposed to Anaplasma within the first 6 months of age.

Genetic variability among populations of the sand fly Lutzomyia (Lutzomyia) longipalpis (Diptera: Psychodidae) from Central America

Eleven Central American populations of Lutzomyia longipalpis (Lutz & Neiva) were analyzed for genetic variation at 16 enzyme loci. The aim was to study the genetic structure among populations within this region and to identify demes that may represent different sibling species. Genotypic frequencies within populations agreed with Hardy-Weinberg expectations, indicating that there were no sympatric sibling species among these 11 populations. Levels of genetic distance between pairs of populations were very low (< 0.02). Some substructing was evident, because after genotypes of all populations mere pooled, 7 of the 16 enzyme loci deviated from Hardy-Weinberg expectations. Estimates of effective migration rates among populations (Nm) were low (3.7), indicating that gene flow was restricted. These data explained observed genetic substructuring when all genotypes were pooled.

Effect of management and inherent factors on birth seropositivity and seroconversion to Babesia bovis in calves in Costa Rica

The relationship between calf characteristics, farm management, seropositivity, and age at seroconversion to Babesia bovis was assessed. A total of 3624 samples obtained from 494 animals on 11 farms was analyzed by an indirect ELISA assay, and individual results classified as positive or negative. The animals were sampled from birth to weaning, beginning in April 1990 and ending in April 1992. We found 59.1% (n = 467) of seropositive neonatal calves (mean age 4.4 days). Using a logistic binomial regression model as the analytical method for predicting the likelihood of calf seropositivity, we found that the following factors were related to seroconversion at birth: time to colostrum consumption, place of birth, calving history, parity (number of lactations), and ecological life zone. To analyze the effect of management factors on time to seroconversion, we used the Proportional Hazards method. In this model the pattern of seroconversion was different for the type of production system. Calves from dual-purpose farms seroconverted earlier than calves from cow-calf farms.

Epizootiologic instability of bovine populations against Babesia bovis (Piroplasmida:Babesiidae) in the region of Poas, Costa Rica

In Poás (Costa Rica), more than 78% of the cattle population is susceptible to Babesia bovis (Babes, 1888) which indicates that care should be taken during animal movement to avoid tick exposure. Seroprevalence is less than 22%; the frequency distribution of antibody titers is presented. Significant differences (p < 0.05) were observed in the distribution of seropositive animals between ecological zones. Lower mountain rain forest and lower mountain wet forest presented higher risk for seropositivity. Based on the serological characteristics of the herds and the frequency of clinical cases, it is suggested that the cattle situation in the area is epidemiologically unstable for B. bovis.

Seasonal incidence and hemoparasite infection rates of Ixodid ticks (Acari: Ixodidae) detached from cattle in Costa Rica

To determine the tick species hindering the cattle industry in Costa Rica and to assess infection rates of ticks with three important hemoparasite species, cattle were monitored during a period of six months (October 1992-March 1993). Four farms were located in the dry pacific region of the canton of Tilarán and a fifth farm on the slopes of the Poás volcano in a cool tropical cloud-forest ecosystem. On each farm 3 to 5 animals of 6 to 24 months of age were selected at random. All ticks were removed on a monthly basis from the right half side of each animal, while the site of attachment was recorded. Ticks were counted and differentiated according to species, developmental stage and sex. Moreover, engorged female ticks were assayed for the presence of Babesia bigemina, Babesia bovis and Anaplasma marginale using the polymerase chain reaction (PCR) multiplex system. Two species of ticks, Amblyomma cajennense and Boophilus microplus, were encountered on the cattle in the Tilarán region and one species, B. microplus, was detected in the Poás region. Two to ten times as many ticks were encountered in the Tilarán region than in the Poás region, which is in accordance with a stable enzootic protozoan disease situation in the former region and an unstable epizootic situation in the latter region. Nymphal and adult stages of both tick species were present in largest numbers on the ventral parts of the animals. PCR analysis of entire ticks indicated very high infection rates with hemoparasites of veterinary importance. This was in accordance with high seroprevalence rates in the hosts.

Phlebotomines (Diptera: Psychodidae) collected at a Costa Rican dairy farm in a vesicular stomatitis endemic area

This study determined the species composition of sand flies in a vesicular stomatitis endemic area, at Carrizal, Alajuela, Costa Rica. Eight species were collected as follows: Lutzomyia volcanensis (Fairchild & Hertig), L. shannoni (Dyar), Lu. pia (Fairchild & Hertig), L. sanguinaria (Fairchild & Hertig), L. youngi Feliciangeli & Murillo, L. longipalpis (Lutz & Neiva), L. serrana (Damasceno & Arouck), and L. gomezi (Nitzulescu).

Lutzomyia longipalpis is a species complex: genetic divergence and interspecific hybrid sterility among three populations

The sand fly Lutzomyia longipalpis is the vector of Leishmania donovani chagasi in Latin America. An analysis of genetic variability at 27 enzyme coding loci among three laboratory populations of Lu. longipalpis revealed substantial genetic polymorphism. Levels of genetic distance between all pairwise comparisons of colonies were very high, and consistent with those previously reported among separate species in the genus Lutzomyia. Between 7% and 22% of the loci studied were diagnostic for any two of the colony populations. Experimental hybridization between colonies resulted in the production of sexually sterile male progeny. Our results provide strong evidence that Lu. longipalpis exists in nature as a complex of at least three distinct species. The possible effects of colonization on the genetic makeup of laboratory populations is considered in extending our results to natural populations.

A programme for computer aided identification of phlebotomine sandflies of the Americas (CIPA)--presentation and check-list of American species

The CIPA programme is a collaborative project including two entomologists from France and seven from South and Central America countries. Its objective is the development of an expert system for computer aided identification of phlebotomine sandflies from the Americas. It also includes the formation of data bases for bibliographic, taxonomic and biogeographic data. Participant consensus on taxonomic prerequisites, standardization in bibliographic data collections and selection of descriptive variables for the final programme has been established through continuous communication among participants and annual meetings. The adopted check-list of American sandflies presented here includes 386 specific taxa, ordered into three genera and 28 sub-genera or species groups.

Proposition of a standard description for phlebotomine sandflies. CIPA Group

In order to be comparable, and efficient, the descriptions need to be as complete as possible and realized according to the same parameters. In this respect, we present the standard description of Phlebotomine sandflies elaborated by an American network of entomologists in a collaborative program dedicated to the creation of a Computer Aided Identification Program for Phlebotomine Sandflies of South and Central America (CIPA programme).

[Characteristics of the venoms and digestive secretions of Aphonopelma seemanni and Sphaerobothria hoffmanni (Araneae: Theraphosidae) of Costa Rica]

A comparison of some components of the venoms of two Costa Rican tarantulas, Aphonopelma seemanni (Cambridge) and Sphaerobothria hoffmanni (Karsch) by polyacrylamide gel electrophoresis shows patterns similar to those of Dugesiella hentzi (Girard), a North American tarantula. The digestive secretions have proteins that do not enter the 15% gels; thus no bands are observed. The method used by the tarantulas to consume their prey involves the action of both the venom and the digestive secretions. The percent protein, pH, proteolytic activity and hemolytic activity of venom and digestive secretions of both species were determined, and a high proteolytic activity for digestive secretions was found.

[Local effects of the external secretions of Sphaerobothria hoffmanni (Araneae: Theraphosidae) from Costa Rica]

The local effects induced as a consequence of applications of four external secretions from the spider Sphaerobothria hoffmanni were recorded. Macroscopic lesions were not found; the only local effect microscopically observed was a weak necrosis in the skeletal muscle in mice.

[The micronecrotic effect of the venom of Aphonopelma seemanni (Araneae: Theraphosidae) of Costa Rica in the white mouse]

The venom of female spiders (Aphonopelma seemanni) induces necrosis of skeletal muscle in mice. This effect was demonstrated by histology and by the increase in the plasma levels of the enzyme creatine kinase (CK).

Dermic peripheral microangiopathy in plasmo-proliferative disorders

Skin biopsy specimens from 12 patients with plasmo-proliferative disease (myeloma and macrogobulinemia) were histopathologically and histochemically examined. In all the cases studied (by a biopsy obtained from the hand) there were alterations in the dermal microvasculature characterized by thickening of the PAS-stained basal membrane, endothelial swelling and proliferation with partial obliteration of the vascular lumen. The lesions were morphologically similar to those found in diabetic and paralymphomatous microangiopathy but in the present investigations greater endothelial proliferation has been observed. We did not find any lesions in the healthy control group. Different immunological, metabolic and hyperviscosity mechanisms are discussed. It is interesting to report that the results for blood coagulation and carbohydrate metabolism were normal; hyperviscosity was found in the serum of the patients examined, and in 3 cases cryoglobulinemia was also found. It will be interesting to carry out further investigations on the different pathogenic and biological aspects of the skin microvascular lesions in plasmo-proliferative diseases in order to increase our knowledge of the microcirculation in immunologic malignant disorders.