Shedding and characterization of gastrointestinal nematodes of growing beef heifers in Central Texas

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Bos indicus crossbred females had higher fecal eggs as calves than as yearlings.

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More Bos indicus background had higher eggs per gram of feces through 1 year of age.

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Cooperia and Haemonchus species predominated through 1 year of heifer age.

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Ostertagia and Trichostrongylus species were detected mostly after 1 year of age.

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Eggs per gram of feces correlated with few production traits of heifers.

Gastrointestinal nematodes (GIN) do not detrimentally affect cattle to the extent of small ruminants. However, they are developing resistance to drugs used to treat them. Genetic strategies to control the nematodes and/or their detrimental effects could be a sustainable alternative to treatment with drugs. An essential first step in development of such a strategy is characterization of nematode populations in commonly used breed types of cattle in local conditions. Fecal egg counts (FEC) were obtained every two months on a cohort of 53 crossbred Nellore-Angus heifers grazing Central Texas pastures from an average heifer age of 3 months to approximately 2 years of age. For 10 of those 12 sets of samples, coprocultures were set up to characterize gastrointestinal nematode species present. Heifers were ½ Nellore ½ Angus (n = 18) or ¾ Angus ¼ Nellore (n = 35). They were born in the spring of 2014 to cows that were from 3–5 years old. They were maintained as a group throughout weaning, postweaning, exposure to bulls as yearlings, and as pregnant cows through the birth of their first calves. An interaction of breed group with sampling time (P < 0.0001) highlighted favorable FEC of ¼ Nellore heifers as compared to ½ Nellore in all but two sampling times. Fecal egg count means were, in general, higher for heifers of both groups in sampling times up to one year of age. Season effects on FEC may be important, but the effect of age may have obscured their detection. There were few significant correlation coefficients for FEC traits with a variety of production traits of these females. Average FEC residuals were positively correlated (r = 0.28 and 0.41; P < 0.05) with winter coat shedding score evaluated at approximately 17 and 24 months of age. Residual correlations of average FEC with calf weaning weight and incidence of shedding with calf age at weaning (r> 0.3) may be indicative of the increased susceptibility of females that lactate heavily or longer to internal parasite infection. Proportions of GIN genera by sampling day differed from χ2 expectation (P < 0.0001). Cooperia and Haemonchus species were detected in large proportions in sampling dates that corresponded to heifers less than one year of age. Ostertagia and Trichostrongylus species predominated in sampling dates after heifers reached one year of age.

Ranch-management factors associated with antibody seropositivity for Neospora caninum in consignments of beef calves in Texas, USA

A study was conducted with a 1998 retained-ownership population of Texas (USA) beef calves to determine the ranch-management practices associated with calf seroprevalence to Neospora caninum. Management practices of 76 Texas ranches that consigned 760 calves to a retained-ownership feedlot program were reviewed from a mailed questionnaire. Ninety-nine of 760 (13%; 95% CI, 9.4%, 17.7%) calves were positive to N. caninum and 59% of the ranches consigned at least one positive calf. In the logistic multiple-regression model which controlled for overdispersion, increased odds of calf-level seropositivity was associated with seasonal calving patterns, with stocking>1cow/calfunit/2.2ha, using a round-bale feeder, allowing wildlife access to the weaning supplement, and self-reared replacement heifers. However, decreased odds of seropositivity was associated with using a cattle-working dog and with using a self-contained cattle feeder. There was substantial overdispersion due to ranch.

Elevated parathyroid hormone-related protein and hypercalcemia in two dogs with schistosomiasis

Two adult dogs were evaluated for hypercalcemia. Diagnostic evaluation identified elevated parathyroid hormone-related protein (PTHrP) and presumptive humoral hypercalcemia of malignancy. At necropsy, schistosomiasis was diagnosed. North American schistosomiasis is caused by Heterobilharzia americana. Clinical findings may include dermatitis, coughing, diarrhea, and anorexia. Clinicopathological findings may include hypercalcemia, hyperglobulinemia, hypoalbuminemia, anemia, and eosinophilia. Diagnosis by fecal examination is difficult. Praziquantel or fenbendazole treatment may be curative or palliative. These are the first reported cases of hypercalcemia with elevated PTHrP in animals without diagnosed malignancy. Elevation of PTHrP has not been previously reported in hypercalcemic humans or in animals with granulomatous inflammation.

Spatial associations among density of cattle, abundance of wild canids, and seroprevalence to Neospora caninum in a population of beef calves

OBJECTIVE

To determine the epidemiologic plausibility of a sylvatic transmission cycle for Neospora caninum between wild canids and beef cattle.

DESIGN

Spatial analysis study.

ANIMALS

1,009 weaned beef steers from 94 beef herds in Texas.

PROCEDURE

Calves were grouped on the basis of seroprevalence for N caninum and ecologic region in Texas. The Morans I test was used to evaluate spatial interdependence for adjusted seroprevalence by ecologic region. Cattle density (Number of cattle/259 km2 [Number of cattle/100 mile2] of each ecologic region) and abundance indices for gray foxes and coyotes (Number of animals/161 spotlight-transect [census] km [Number of animals/100 census miles] of each ecologic region) were used as covariates in spatial regression models, with adjusted seroprevalence as the outcome variable. A geographic information system (GIS) that used similar covariate information for each county was used to validate spatial regression models. Results-Spatial interdependence was not detected for ecologic regions. Three spatial regression models were tested. Each model contained a variable for cattle density for the ecologic regions. Results for the 3 models revealed that seroprevalence was associated with cattle density and abundances of gray foxes, coyotes, or both. Abundances of gray foxes and coyotes were collinear. Results of a GIS-generated model validated these spatial models.

CONCLUSIONS AND CLINICAL RELEVANCE

In Texas, beef cattle are at increased risk of exposure to N caninum as a result of the abundance of wild canids and the density of beef cattle. It is plausible that a sylvatic transmission cycle for neosporosis exists.

Association of serologic status for Neospora caninum with postweaning weight gain and carcass measurements in beef calves

OBJECTIVE

To determine the seroprevalence for Neospora caninum in a population of beef calves in a feedlot and the association of serologic status with postweaning weight gain and carcass measurements.

DESIGN

Longitudinal observational study.

ANIMALS

1,009 weaned beef steers from 92 herds.

PROCEDURE

Samples were obtained from all steers at time of arrival at a feedlot. Serologic status for Neospora spp was determined, using an agglutination test. Results of serologic testing were compared with calf growth and carcass data, using multivariate regression with generalized estimating equations.

RESULTS

Of 1,009 calves, 131 (12.98%) were seropositive, and 54 of 92 (58.7%) consignments had > or = 1 seropositive calf. Median within-consignment prevalence for consignments in which there was > or = 1 seropositive calf was 20%. Seropositive status was associated with significant reductions in average daily gain, live body weight at slaughter, and hot carcass weight and an increase in ribeye area-to-hot carcass weight ratio. Seropositive status also was associated with significant increases in cost of treatment and significant reductions in income. Sick seropositive calves had the highest cost of treatment. An economic loss of $15.62/calf was projected for seropositive calves.

CONCLUSIONS AND CLINICAL RELEVANCE

Significant reductions in postweaning weight gain, carcass weight, and economic return were associated with detection of antibodies to N caninum in beef calves in a feedlot.

Evaluation of anthelmintic activity in captive wild ruminants by fecal egg reduction tests and a larval development assay

The effectiveness of anthelmintics was evaluated in four herds of captive ruminants, wapiti (Cervus elaphus), Armenian red sheep (Ovis orientalis), giraffe (Giraffa camelopardalis), and pronghorn (Antilocapra americana), by the use of fecal egg reduction tests (FERTs) and a commercial larval development assay (LDA) designed to evaluate susceptibility or resistance of nematodes to anthelmintics. Haemonchus sp. was the predominant nematode in the red sheep, giraffe, and pronghorn herds, whereas Ostertagia sp. and Trichostrongylus sp. were predominant in the wapiti. The LDA data indicated susceptibility by the worms to benzimidazoles except in the red sheep flock, which showed a high level of resistance. High levels of resistance to levamisole were seen in the worm populations from the wapiti and red sheep, moderate resistance in the pronghorn herd, and susceptibility in the giraffe herd. Worms were susceptible in all four herds to a combination of benzimidazole/levamisole. There was suspected avermectin resistance by Trichostrongylus sp. in the wapiti herd and by Haemonchus sp. in the giraffe. The FERTs agreed with the LDA in showing the Haemonchus in the giraffe was susceptible to fenbendazole and had suspected resistance to ivermectin, whereas Haemonchus in the red sheep and pronghorn were susceptible to ivermectin. There was correlation between the tests evaluating anthelmintics. The LDA is useful as a screening test in the selection of an anthelmintic for use in grazing ruminants, but the effectiveness of a drug in a host species may depend as much on the dose used, and the method of administration, as it does on the parasite's sensitivity to the anthelmintic.

Antigenic, phenotypic and molecular characterization confirms Babesia odocoilei isolated from three cervids

Babesia isolates from an elk (Cervus elaphus canadensis) and a caribou (Rangifer tarandus caribou) with fatal infections were compared to Babesia odocoilei (Engeling isolate) from white-tailed deer (Odocoileus virginianus) by experimental infection, serologic, and small subunit ribosomal RNA (SSU rRNA) gene sequence analysis studies. Both the indirect fluorescent antibody test and immunoprecipitation assays demonstrated antigenic variation among the isolates. Experimental infection studies showed no clinical differences among the isolates. Nucleotide sequence analysis showed that the elk and caribou Babesia sp. isolates possessed SSU rRNA genes with identical sequences to that of B. odocoilei. A phylogenetic tree constructed from SSU rRNA gene sequences shows that B. odocoilei is most closely related to Babesia divergens, both of which branch together in the true babesia clade.

Considerations for the control of equine cyathostomes in arid areas

Internal parasites of horses are ubiquitous but that does not suppose that the level of infection does not vary with climatic conditions. Climate determines the limits of where a parasite species can survive the external environment and weather determines the transmission pattern within the climatic bounds [Levine, N.D., 1963. Adv. Vet. Sci. 8, 215-261]. Arid areas have a more limited exposure potential to important parasites but the level of exposure can nonetheless lead to disease. It must be remembered that, even in arid areas, it does rain and irrigation, overflow from water troughs, dew dripping off buildings and on the vegetation can also provide the medium to allow escape of larval cyathostomes from feces to forage. How horses earn their living is most important in determining the level of exposure to cyathostomes. Recreational grazing, which surely does more for the soul of the owner than for the nutrition of the horse, almost absolutely insures that horses will encounter larvae. To be certain, in arid areas there may be an opportunity for horses to spatially separate grazing and dunging areas but not all horses are so disposed, and even if they are they may not be able to do so.

Parasite diversity and anthelmintic resistance in two herds of horses

Diversity of parasite populations was compared between two herds of horses, one a regularly treated herd the other a feral herd which has bad no anthelmintic treatment for at least 25 years. Eggs obtained from fecal samples of both herds were tested for anthelmintic resistance by use of an in-vitro larval hatch/development assay (LDA), DrenchRite. A fecal egg reduction test was also performed with the domesticated herd using fenbendazole, pyrantel pamoate and ivermectin. Cyathostomes were the predominant group of worms present in both herds. Trichostrongylus axei was seen in both herds, but Strongylus equinus, Strongylus vulgaris, Gyalocephalus capitatus, Poteriostomum spp. and Strongyloides westeri were only found in the feral horses. Larvae of Strongylus edentatus were found in a single domesticated horse. Fecal egg reduction tests with the domesticated herd showed a 32% egg count reduction for fenbendazole, a 93% reduction with pyrantel, and a 99% reduction with ivermectin. From the LDA, anthelmintic resistance was evaluated by determining the resistance ratio of the domesticated herd compared with the feral herd. For benzimidazoles in the domesticated herd, 45% of the cyathostome population was 9.4 times more tolerant than the feral herd's parasite population. The parasite population in the domesticated herd was 1.5 times more tolerant to Levamisole, and 1.7 times more tolerant to the benzimidazole/levamisole combination than the parasite population within the feral herd. 9% of the parasite population in the domesticated herd was 90 times more tolerant to avermectins than the feral herd's parasite population, even though a subpopulation of worms in the feral herd were tolerant to low concentrations of avermectins despite never being previously exposed to this class of anthelmintic.

Comparison of naturally acquired parasite burdens among Florida native, Rambouillet and crossbreed ewes

The response to natural infection by gastrointestinal nematodes was evaluated in three groups of lambing mature ewes: 16 Florida Native; 21 Rambouillet; and 18 1/2 Florida Native x1/2 Rambouillet (F1 generation). Fecal egg counts (FEC), packed cell volume (PCV) and plasma protein levels were determined periodically through a one-year period. The highest FEC was recorded in Rambouillet ewes, with most of the means higher than 1000 eggs per gram (EPG). Florida Native and F1 ewes showed similar trends in FEC, with most of the means below 500 EPG. The highest mean PCV values were recorded in Florida Native ewes, followed in decreasing order by F1 and Rambouillet ewes. F1 ewes showed the lowest plasma protein levels and Florida Natives the highest. Fecal cultures revealed the highest percentages of Haemonchus larvae in Rambouillet ewes (>64%) and the lowest percentages in Florida Native ewes. Florida Native and F1 ewes were more resistant to gastrointestinal nematode infections than were Rambouillet ewes. High negative correlation coefficients between FEC x PCV and FEC x plasma protein levels coincided with peaks in mean FEC of Rambouillet (May and July), Florida Native and F1 ewes (October). This study showed that crossbreeding Rambouillet and Florida Native sheep resulted in the production of F1 ewes resistant against gastrointestinal nematode infections.

Two Theileria cervi SSU RRNA gene sequence types found in isolates from white-tailed deer and elk in North America

Two Theileria cervi SSU rRNA gene sequence Types, F and G, from white-tailed deer (Odocoileus virginianus) and elk (Cervus elaphus canadensis) isolates in North America were confirmed. Previously, nucleotide sequencing through a single variable (V4) region showed the presence of SSU rRNA gene Types F and G in T. cervi isolates from white-tailed deer and an elk. In this study, both sequence types were found in four T. cervi isolates (two from deer and two from elk). Microheterogeneity only appeared in the Type G gene, resulting in Subtypes G1, G2 and G3. Subtype G1 was found in two elk and one white-tailed deer T. cervi isolate; Subtypes G2 and G3 were found in a white-tailed deer T. cervi isolate. The Type F SSU rRNA genes were identical in nucleotide sequence in both elk and white-tailed deer T. cervi isolates. The high degree of conservation in the Type F variable regions may be exploited to design specific oligonucleotide primers for parasite detection by the polymerase chain reaction in cervine or tick hosts.

Nematode burdens and cellular responses in the abomasal mucosa and blood of Florida Native, Rambouillet and crossbreed lambs

This experiment was carried out to compare the worm burden and cellular responses in the abomasal mucosa and blood of Florida Native and Rambouillet lambs and also in animals produced by crosses of these two breeds (generations F1 and F2). Animals were exposed to infection by gastrointestinal nematodes on three different occasions. The first infection was natural, occurring while they were suckling lambs. After weaning, they were kept indoors for 53 days and then were allowed to graze a contaminated pasture for 50 days for a second natural infection. The third infection was an artificial challenge with 6000 Haemonchus contortus infective larvae. The highest mean fecal egg counts (FEC) values were found in Rambouillet lambs followed in decreasing order by F1, F2 and Florida Native lambs. Throughout the trial, most of the high mean packed cell volumes and plasma protein levels were recorded in the F2 lambs; in contrast, most of the low values were found in the Rambouillet lambs. During the natural infection period, the highest percentages of larvae in the fecal cultures of the lambs were Haemonchus. However, high percentages of Trichostrongylus larvae were found particularly in Florida Native lambs. The mean number of blood eosinophils increased after the artificial challenge, reached a peak 21 days after infection and then declined. The highest and lowest blood eosinophil means were recorded in F2 and Florida Native lambs, respectively. The H. contortus burden was significantly higher in Rambouillet and in F1 lambs than in Florida Native and F2 lambs (p < 0.05), while no significant differences were recorded among eosinophil, mast cell and globule leucocyte counts in the abomasal mucosa (p > 0.05). The highest correlation coefficient recorded at the end of this study was between FEC and worm burden (r = 0.7). These two parameters showed a moderate negative correlation with PCV, plasma protein and mast cell counts in the abomasal mucosa. The results obtained in this study indicate that crossbreeding Florida Native and Rambouillet sheep can be a rapid way to combine and improve the characteristics of these two breeds. The parasitological results were promising, however, more studies will be necessary to verify the impact of crossbreeding in other traits.

Serologic and parasitologic survey of the endangered Attwater's prairie chicken

Because conservation biologists have postulated that infectious diseases may have potentiated the endangerment of the Attwater's prairie chicken (Tympanuchus cupido attwateri), free-living prairie chickens were surveyed from all remaining populations for helminthic endoparasites and antibody against the etiological agents of nine infectious diseases. Samples from 4 of 27 adult males were positive for anti-Pasteurella multocida antibody. All other serologic tests were negative (n = 19). We identified Dispharynx nasuta, a parasite previously associated with disease in other grouse from North America, in one of three adult Attwater's prairie chickens examined. Evidence of Trichostrongylus cramae was found for eight of nine suitable samples, which represents the first report of this parasite in prairie grouse. The mean intensity of T. cramae in Attwater's prairie chicken was 1,019.3 (Range = 3-1,906; n = 3). Further work is needed to determine whether P. multocida, T. cramae, or D. nasuta are detrimental to Attwater's prairie chicken populations. If so, conservation biologists could reduce the prevalence and incidence of these parasites and potentially gain more time to address the habitat conditions thought to be the ultimate cause of population declines.

The synlophe and other structural characteristics of Sarwaria bubalis (Nematoda: Trichostrongyloidea) from cattle in Guyana

The synlophe (longitudinal, surface cuticular ridges) of Sarwaria bubalis is described for the first time. It is a tapering lateral synlophe of about 40 ridges. The synlophe of S. bubalis is similar to that of Ostertagia ostertagi but markedly different from that of species of Spiculopteragia and Mazamastrongylus. New information is provided also on the structure of the esophagus and perivulval pores. The esophageal valve is more than twice as long as wide. The bilateral perivulval pores were located 192-267 microns posterior to the vulva and dorsal to the lateral lines. The new information will be useful in a study of the generic level systematics of the Ostertaginae. Sarwaria bubalis appears to be well established in tropical South America where it infects its normal host, the Asian water buffalo Bubalus bubalis, as well as domestic cattle Bos taurus and mixed breed cattle B. taurus x Bos indicus.

Scrotal hydrocele secondary to ascites in 28 bulls

Twenty-eight of 104 mature bulls in a herd were examined to determine the cause of scrotal enlargement. Ascites was determined as the source of a transudate that accumulated in and expanded the scrotal vaginal cavity to induce a scrotal hydrocele. In our experience, scrotal hydrocele in mature bulls usually is caused by the accumulation of fluids in the scrotal vaginal cavity without evidence of local inflammation or traumatic lesions. In the bulls reported here, ascites was associated with intestinal edema that was tentatively attributed to a hypersensitivity reaction to gastrointestinal nematodes. Ascites in mature bulls with scrotal hydrocele in which primary lesions of the scrotum and scrotal contents are not detected should induce practitioners to perform additional diagnostic procedures to determine the cause of the fluid.

Ocular Halicephalobus (syn. Micronema) deletrix in a horse

Ocular contents from a horse with a 4-week history of severe unilateral uveitis were submitted for histopathologic examination. A severe unilateral granulomatous chorioretinitis with intralesional Halicephalobus deletrix was diagnosed. The horse developed progressive neurologic signs several days following the surgery to remove ocular contents and implant a prosthesis and was subsequently euthanatized. A severe multifocal granulomatous encephalitis with intralesional H. deletrix, localized primarily to the optic chiasm, thalamus, and brain stem, was diagnosed from tissues acquired at necropsy. The other eye was not affected. This is the first report of ocular parasitism by H. deletrix and suggests possible systemic dissemination from a primary site in the eye.

Enzyme-linked immunoelectrotransfer blot analysis of excretory-secretory proteins of Fascioloides magna and Fasciola hepatica

Fasciola hepatica is a parasite of cattle (Bos taurus), but not of white-tailed deer (Odocoileus virginianus), while Fascioloides magna is a parasite of white-tailed deer which also infects cattle as dead-end host. Adult parasites were collected from naturally infected white-tailed deer or cattle. Excretory-secretory proteins (ESP) were obtained from each parasite. Protein banding patterns were analysed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and probed using sera from experimentally infected deer of cattle using enzyme-linked immunoelectrotransfer blot (EITB, also known as Western blot) analysis. Protein banding patterns of the two species were different. EITB analysis of Fascioloides magna ESP using sera from Fascioloides magna infected deer or cattle identified three bands of approximately 17, 22 and 27 kDa of which the 27 kDa antigen cross-reacted with sera from Fasciola hepatica infected cattle. EITB analysis of Fasciola hepatica ESP probed with sera from Fasciola hepatica infected cattle identified three bands of approximately 15, 26 and 46 kDa. The 46 and 26 kDa ESP cross-reacted with sera from Fascioloides magna infected cattle, but not with sera from Fascioloides magna infected deer. The band at 15 kDa which reacted specifically for Fasciola hepatica infected cattle sera consisted of two protein bands close to each other as seen on the SDS-PAGE gel. The EITB reaction at approximately 17 kDa and 22 kDa of Fascioloides magna ESP, and at approximately 15 kDa of Fasciola hepatica ESP can be used for species specific diagnosis.

Culture isolation and partial characterization of a Babesia sp. from a North American elk (Cervus elaphus)

Three North American yearling elk (Cervus elaphus) died with clinical symptoms suggestive of babesiosis. Babesia sp. organisms similar in morphology to B. odocoilei of white-tailed deer (Odocoileus virginianus) were observed in Giemsa-stained blood films from one of the elk. Continuous cultures of the parasite were established. Antiserum raised against the elk Babesia sp. isolate was compared to B. odocoilei specific antiserum in an immunofluorescent antibody assay; we found evidence of differences in reactivity to several Babesia spp. isolated from wildlife and domestic ruminants. Cultured parasites from the elk were not infective to either intact or splenectomized Bos taurus steers.

Use of bait containing triclabendazole to treat Fascioloides magna infections in free ranging white-tailed deer

Triclabendazole-medicated corn bait was given to white-tailed deer (Odocoileus virginianus) on the Welder Wildlife Refuge, Sinton, Texas (USA), at a dose of 11 mg/kg body weight per deer per day for seven days, for control of Fascioloides magna. Medicated bait was offered for one week each during the winters of 1987, 1988, and 1989. Deer collected from treated areas, from baited control and from unbaited control areas were examined before the start of the study in 1987, and four weeks after the end of the baiting period in each of three years. Prior to the study, prevalence of fluke infection was 68%. After treatment with triclabendazole medicated corn, 13 (56%) of 23 deer collected were infected with flukes of which 15% had live parasites; this was evidence for therapeutic treatment. Of the deer collected in the baited and unbaited control areas, 63% and 80%, respectively, were infected only with live flukes. Prevalence of live flukes in deer was significantly (P < 0.05) lower in the treatment pasture than in the baited or unbaited control areas in each of the three years. Efficacy of the baiting system over the three years was 63% when comparing the treatment area and the baited control area.

Ultrastructure of Hepatozoon canis in the dog

The ultrastructure of several stages of Hepatozoon canis found in dogs with clinically diagnosed infections was determined using transmission electron microscopy. Stages were found in skeletal muscle tissue that corresponded to the 'onion skin' cyst stage, as described at the light microscopic level, and were composed of an electron-transparent material that appeared to radiate from a central core. Larger cysts, walled off by fibroblasts, contained a transformed host cell located centrally within them. The parasitic stage within these transformed cells contained numerous organelles including mitochondria and Golgi apparatus, and was singularly nucleated. In cardiac muscle, a meront was observed which produced merozoites by ectomerogony. Adjacent to this meront was a granuloma containing merozoites within mononuclear phagocytes which may either serve as a reservoir of parasites for reinfection of the host or differentiate into the circulating gamont stage of the parasite. Gamonts were found within parasitophorous vacuoles inside circulating neutrophils. They had a condensed cytoplasmic appearance and were extremely electron dense with respect to other observed parasite stages. In vitro cultivation of parasitized neutrophils resulted in the appearance of a stage of the parasite with altered ultrastructure compared with gamonts found in circulating neutrophils. This stage was judged to be a possible gamete stage of the parasite.

Protozoal abortion in a herd of cattle concurrently infected with Hammondia pardalis

Protozoal infection was diagnosed as the cause of abortion in a large drylot dairy herd located in northeastern Mexico. Diagnosis was made on the basis of finding encephalitis, myocarditis, protozoal cysts, and protozoal tachyzoites in aborted fetuses. The blended ration fed to the cows had been contaminated by the feces of a large resident population of feral domestic cats that used components of the blended ration for den sites (stored hay) or as a latrine (grain). The cows that aborted contained tissue phases of a protozoan infective for domestic cats. The morphologic features of the oocyst and biologic features of the protozoan were identical to those of Hammondia pardalis.

Longistrongylus curvispiculum (Nematoda: Trichostrongyloidea) in free-ranging exotic antelope in Texas

Longistrongylus curvispiculum was recovered from free ranging sable (Hippotragus niger), addax (Addax nasomaculatus) and biesa oryx (Oryx beisa) on two ranches in central Texas (USA). These nematodes represented a small portion of the total abomasal worm burden dominated by Haemonchus contortus. Female L. curvispiculum easily could be confused with other ostertaginae, but the spicules of the males were diagnostic.

Spiculopteragia spiculoptera and S. asymmetrica (Nematoda: Trichostrongyloidea) from red deer (Cervus elaphus) in Texas

Specimens of Spiculopteragia spiculoptera and S. asymmetrica were recovered from the abomasa of five of ten naturally infected red deer (Cervus elaphus) in Texas (USA). Female specimens of Spiculopteragia were present in all five animals. Male specimens of S. spiculoptera and S. asymmetrica were present in one of five and three of five red deer, respectively. Spiculopteragia spiculoptera has not previously been recognized in the United States and the present report constitutes the first records of Spiculopteragia spp. in red deer from North America. It is likely that species of Spiculopteragia have been introduced to North America with the import of exotic cervids on several occasions. Focal populations of these nematodes have been established in North America; however, distribution of the parasites likely coincides with areas of residence of introduced populations of red deer and fallow deer (Cervus dama) in the Nearctic.

Lynxacarus radovskyi infestation in a cat

An adult domestic short-hair cat from south Texas was examined because of excessive dandruff on the back, neck, thorax, and hind limbs. Removal of a few hairs for microscopic evaluation revealed Lynxacarus radovskyi, the cat fur mite. The small (< 0.5 mm) mite could be readily identified by its laterally compressed body and its characteristic grasping of the hair shaft between the gnathosoma and palpi. Thus far, this mite has been identified as a parasite of cats in warm, humid environments. The number of parasites and apparent discomfort in cats varies considerably, from massive infestation with little discomfort to few mites and marked pruritus. Acaricides that are effective against other ectoparasites of cats apparently are effective in controlling L. radovskyi.

Anthelmintic resistance

In populations of livestock in which anthelmintics have become the only means of control, individual worms in some species of helminths evade the effects of specific anthelmintics. If these resistant individuals are selected (by removing the susceptible individuals in the population) then the resistant worm population on individual farms becomes dominant in both numbers and effect. This selection of anthelmintic resistant populations is most often reported in equids and small ruminants (the hosts in which anthelmintics are used most frequently). There is little evidence of anthelmintic resistance by Ostertagia in cattle but an understanding of the problem in other grazing species may aid in delaying its onset. Benzimidazole/phenothiazine resistance by small strongyles in horses in widespread. Resistance by various geographic strains of Haemonchus, Teladorsagia and Trichostrongylus against all of the commonly used classes of anthelmintics in small ruminants has been verified. The failure of levamisole to remove adult Ostertagia ostertagi from cattle has been reported in several geographical areas. Resistance is an individual farm problem and each premise has to be evaluated as to which anthelmintics can be used. Drug rotation, especially rapid rotation (less than 1 year) selects for multiple drug resistance. Epidemiologic treatment selects for resistance, but if properly used, requires considerably fewer treatments to prevent disease and the development of resistant populations will be slowed. A combination of strategic and tactical treatments along with evaluation of anthelmintics will be required to enable producers to raise livestock in maximum production units.

Diffuse cutaneous leishmaniasis in a cat

An adult long-haired domestic cat native to South Texas developed signs consistent with diffuse cutaneous leishmaniasis. Cutaneous leishmaniasis, caused by Leishmania mexicana, was initially diagnosed from lesions confined to the left ear. A radical pinnectomy was done and the cat was returned to its owner. Two years later, lesions developed at the stump, and lesions later developed on the cat's muzzle and nasal mucosa. All of the lesions contained numerous L mexicana amastigotes. Several treatment regimens were attempted, but without evidence of resolution. The cat was tested multiple times for evidence of impaired immunologic competence and was found to be normal. The cat failed to respond to Leishmania antigen given interdermally (Montenegro test) on several occasions. On one occasion, however, there was partial regression of the lesions following the Montenegro test. Cats in areas endemic for cutaneous leishmaniasis (South Texas) may serve as sentinels for the agent. The epidemiology of the infection in this area is largely unknown, as is the importance of cats in the spread of disease.

Efficacy of two formulations of albendazole against liver flukes in cattle

Albendazole (10 mg/kg of body weight) was administered as a drench suspension or as a feed additive to 24 cattle with naturally acquired infections of Fasciola hepatica and Fascioloides magna. Cattle were euthanatized 16 to 30 days after treatment, and the number of viable flukes was counted. Viable F hepatica and F magna were decreased by 91.4% and 70.6% for drench administration and by 82.9% and 71.9% for the feed additive treatment, respectively. There was no significant difference between the efficacy of the 2 formulations in decreasing viable fluke numbers, compared with untreated controls.

Eosinophilic gastroenteritis with encapsulated nematodes in a horse

A 3-year-old Quarter Horse gelding admitted for evaluation of weight loss, signs of depression, and dermatitis of the coronary bands was found to have eosinophilic gastroenteritis. Intralesional nematodes identified as Strongylus edentatus were seen in multiple microscopic sections of the small colon, suggesting a parasitic cause of the disease.

Resistance to ivermectin by Haemonchus contortus in goats and calves

Efficacy of ivermectin on susceptible or resistant populations of the parasitic nematode Haemonchus contortus was determined in cattle and goats held in a barn. Goats were each infected with 3000 infective, ivermectin-susceptible or -resistant H. contortus larvae on day 0 and reinfected with 2000 infective larvae on day 24. Goats were treated orally with 600 micrograms kg-1 ivermectin on day 31. No significant differences were detected in blood packed cell volume (PCV) or total protein (TP), prepatent period, or epg among the four groups of goats that were each infected with one of four parasite strains (one susceptible, three resistant). There were no differences among the four parasite strains in the numbers of infective larvae that developed to the third larval stage from fecal cultures or in the viability of cultured infective larvae when held in the laboratory at 27 +/- 1 degrees C for 14 weeks. After treatment with ivermectin, there were significant differences among the parasite strains in PCV, TP, and epg. Total worm counts were reduced by 94 to 97% with three times the recommended dose. Immature and adult Skrjabinema ovis were also present in two treated goats. In a second test, one goat infected once with 10,000 infective larvae of a resistant strain of H. contortus and then treated with nine doses of ivermectin, increasing from 500 to 2000 micrograms kg-1 over a period of 133 days, had 35 adult worms at necropsy. In a third test, three calves were readily infected with an ivermectin-resistant strain of H. contortus from goats.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of moxidectin against an ivermectin-resistant strain of Haemonchus contortus in sheep

The efficacy of moxidectin was determined against ivermectin-susceptible and resistant strains of Haemonchus contortus. At the onset of the trial, 40 lambs were each infected with 5000 third stage larvae of one of two strains of Haemonchus contortus. The lambs were randomly sorted into eight treatment groups 28 days post-infection and were treated as follows: Group 1, susceptible strain with no treatment; Group 2, resistant strain with no treatment; Group 3, susceptible strain treated with 0.2 mg moxidectin kg-1 body weight; Group 4, resistant strain treated with 0.2 mg moxidectin kg-1; Group 5, resistant strain treated with 0.4 mg moxidectin kg-1; Group 6, susceptible strain treated with 0.2 mg ivermectin kg-1; Group 7, resistant strain treated with 0.4 mg ivermectin kg-1; Group 8, resistant strain treated with 0.8 mg ivermectin kg-1. The lambs were killed 1 week post-treatment. Comparisons were made among groups based on the number of eggs per gram of feces on the day of treatment and the numbers of worms recovered from each lamb. Both moxidectin and ivermectin were effective in removing susceptible Haemonchus with efficacies of 100% and 99.7%, respectively. The efficacy of moxidectin against the resistant strain was 99.9% and 100% at 0.2 mg kg-1 and 0.4 mg kg-1, respectively, whereas there were only 38.8% and 53.1% efficacies in the lambs treated with 0.4 mg ivermectin kg-1 and 0.8 mg kg-1 body weight, respectively.

Effect of milbemycin oxime against Ancylostoma caninum in dogs with naturally acquired infection

Twenty-six mixed-breed (14 males, 12 females) dogs were used in a double-blind study to evaluate the effect of milbemycin oxime against naturally acquired infection with Ancylostoma caninum. Dogs were ranked and paired, on the basis of number of hookworm eggs/g of feces, and treatment was randomly assigned. Each dog was given either the study drug or placebo (1 tablet/11.4 kg [0.5 mg/kg] of body weight). Eggs per gram of feces enumeration was done on days 3 and 7 after treatment, and dogs were euthanatized on day 7. On day 3, 5 of the 13 dogs in the milbemycin-treated group had hookworm eggs in the feces (results of the McMaster test). In these dogs, mean number of eggs per gram of feces had decreased markedly (from 5,289 to 452) and, by day 7, was 114. At necropsy, 16 A caninum adults were recovered from 2 of the milbemycin-treated dogs. On day 3, 12 of the 13 dogs in the placebo-treated group had hookworm eggs in the feces. Mean number of eggs per gram of feces in these dogs decreased slightly (from 5,243 to 2,646), but did not decrease further by day 7. A mean number of 54.4 A caninum adults was recovered from 12 of the 13 placebo-treated dogs at necropsy. Milbemycin oxime had 97.8% efficacy against A caninum. Results also indicated that milbemycin oxime may be effective against Trichuris vulpis, but not against Dipylidium caninum.

Efficacy of nitroscanate against naturally acquired infection with Ancylostoma caninum, Dipylidium caninum, and Trichuris vulpis in dogs

Eighteen dogs with naturally acquired helminth infections were used to evaluate the efficacy of nitroscanate against Ancylostoma caninum, Dipylidium caninum, and Trichuris vulpis. Approximately 15 minutes before treatment, the dogs were given 100 to 200 g of canned dog food. Ten dogs were treated with nitroscanate (50 mg/kg of body weight, PO), and 8 dogs were given placebo tablets PO. The dogs were euthanatized and necropsied 10 days after treatment and helminths were recovered from the small intestine and cecum. On the basis of the number of worms recovered from treated dogs vs the number recovered from control dogs, we determined the efficacy of nitroscanate to be 99.6% against A caninum, 99.8% against D caninum, and 0% against T vulpis.

Nutritional and dietary interrelationships with diseases of grazing beef cattle

This article describes current methods of controlling acute bovine pulmonary emphysema (ABPEE) and edema, lungworm and gastrointestinal nematodes, and bloat in grazing beef cattle. Success in handling outbreaks of these conditions and in their prevention depends on an understanding of their epidemiology and pathogenesis. Supplementation with ionophore antibiotics is effective in prevention of ABPEE and bloat and may also prevent other diseases of cattle that graze lush pastures.

Naturally occurring apicomplexan acute interstitial pneumonitis in thick-billed parrots (Rhynchopsitta pachyrhyncha)

This report describes acute interstitial pneumonitis due to an apicomplexan parasite with schizogony in endothelial cells of pulmonary vessels accompanied by early and metrocyte stages of sarcocysts in the heart of a thick-billed parrot (Rhynchopsitta pachyrhyncha). The pattern of this disease is similar to that of the acute phase (approximately 10-15 days postinoculation) of experimental infections of budgerigars, Melopsittacus undulatus, with high doses of sporocysts of Sarcocystis falcatula.

Efficacy of triclabendazole against fascioloidiasis (Fascioloides magna) in naturally infected white-tailed deer (Odocoileus virginianus)

The efficacy of triclabendazole was evaluated in the treatment of naturally acquired Fascioloides magna infections in white-tailed deer (Odocoileus virginianus). Twenty white-tailed deer were captured on the Welder Wildlife Refuge (Sinton, San Patricio County, Texas, USA) and maintained in a 64 x 64 m deer enclosure. Ten deer were given a 5% suspension of triclabendazole orally at a dosage of 10 mg/kg body weight and 10 deer were given a placebo. Three wk later the deer were euthanized and examined for parasites. At necropsy 19 deer were infected. All specimens of F. magna from the tissues of the triclabendazole treated deer were dead or severely affected by the drug as indicated by changes in their size, color, movement and texture relative to those from control deer. The drug was considered 100% effective against this parasite. Adverse reactions of the deer to the drug were not observed.

Use of the sustained-release morantel bolus in stocker calves in southern United States

Two groups of 21 mixed-breed heifers were wintered on separate permanent pastures. Each heifer from one group was administered a sustained-release morantel bolus on October 7 (day 0), and the other group remained as untreated controls. Body weights were determined and fecal samples were taken at 28-day intervals. At the onset of the trail and at every 56 days, 6 heifers were removed from each group for slaughter to determine the developmental stages and the number of gastrointestinal nematodes. In addition, 3 tracer calves that were free of gastrointestinal nematodes were released on each pasture for 28 days at the beginning of the trail and after the last experimental-group calves had been removed. The 6 calves slaughtered on day 0 of the trail had a mean of 5,544 gastrointestinal nematodes. Tracer calves released on day 0 and removed on day 28 of the trial acquired 31,143 and 30,530 gastrointestinal nematodes from the pastures containing the treated and control heifers, respectively. Throughout the trial, the number of nematodes in the control calves increased at each sampling date (mean, 126,168 worms), whereas the mean number of worms in the treated heifers was 45,458. Tracer calves placed in the pastures after the 168-day trail acquired significantly more worms (9,632 vs 2,899; P less than 0.05) from grazing the pastures with control heifers than from grazing the pastures with treated heifers. Counts of eggs per gram of feces were significantly different (P less than 0.01) between the 2 groups from day 28 through day 112.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of Various Staining Procedures in the Identification ofHepatozoon canisGamonts

The staining characteristics of gamonts of Hepatozoon canis in peripheral blood smears were evaluated. Three stains, Diff-Quik stain, Giemsa stain and a modification of the naphthol-ASD-chloroacetate esterase stain, were compared. The staining characteristics of the infected cell and the parasite were different in each stain used. The modified naphthol-ASD-chloroacetate esterase stain showed the most difference between the infected and noninfected cells, as well as a difference in staining characteristics of the parasite nucleus from those of the host nucleus. Although the parasite was identified with all stains, a definitive diagnosis was more easily obtained with the naphthol-ASD-chloroacetate esterase stain.

Hepatozoon sp. in wild carnivores in Texas

Twelve coyotes (Canis latrans), three bobcats (Lynx rufus) and six ocelots (Felis pardalis) from the Gulf Coast of Texas were infected with Hepatozoon sp. The geographic distribution of infected wild animals coincides with the highest prevalence of Hepatozoon canis infection in domestic dogs for which the wild species may act as a reservoir.

Impact of internal parasites on beef cattle

Internal parasitism is a pervasive constant that reduces returns in beef cattle production. Parasitism may influence production sufficiently so that data derived investigating performance response will be erroneous. The interaction of internal parasites of cattle with other facets of their lives makes it imperative that more parasite research be done on cattle to consider their impact. Results of trials designed to determine forage production at various stocking densities may not reflect the nutritive value of the forage, but instead the severity of parasite exposure. Relative resistance or susceptibility to certain parasites vary with the breed of livestock and the species of parasite. Extensive work to evaluate the ability of various breeds and sires to influence parasitic numbers has been conducted in sheep but not in cattle. Some parasite trials have ignored the effects of nutrition on the establishment and retention of parasites. This becomes especially important where multiple parasite exposure may occur. Susceptible cattle, even on an optimal diet, will become parasitized, but if reexposed to the same species of parasite, cattle on an optimal diet may be able to resist reinfection, whereas those on deficient diets will not.

Liver fluke infections of cattle in Mali. An abattoir survey on prevalence and geographic distribution

Six hundred and ninety two cattle, slaughtered in various abattoirs in Mali between August 1983 and November 1984 were examined for evidence of Fasciola gigantica and Dicrocoelium hospes infections. A great variation in geographic prevalence was observed. Sufficient knowledge was acquired to demonstrate both the importance of fascioliasis in some areas and also the high prevalence of D. hospes in other areas. We suggest that the difference in prevalence from one geographic area to another is influenced by local climatic conditions, presence or absence of rivers and lakes, and differences in livestock management practices by various ethnic groups.

Dermal leishmaniasis in a Texas cat

Leishmaniasis was diagnosed by demonstrating amastigotes of Leishmania from dermal lesions on the ear of a male long-haired domestic cat from Uvalde, Texas. Leishmania from the cat were propagated in Syrian hamsters, bovine macrophages, and in NNN medium. The organism, in the L. mexicana complex, is apparently the same as that reported from recent human cases in the same area.

Epidemiology and control of parasites in warm climates

The kind of parasites a horse acquires depends upon its environment. Because patterns of transmission vary greatly with climate and management, no one worming program has universal applications. This article discusses epidemiology and control of equine parasites in the southern United States, where climates vary from warm temperate to subtropical and from humid in the southeast to arid in the southwest.