In vitro study of disinfectants on the embryonation and survival of Toxascaris leonina eggs.

The effect of six available and commercial disinfectants on the embryonation and larval development of Toxascaris leonina eggs was studied. Dettol® and Virkon® both induced a 100% reduction in larval development (P ≤ 0.05). Dettol® resulted in deformed eggshells and a halt in embryonal development at 1 week post exposure. All Virkon®-treated eggs showed an early embryonic lysis 24 h post exposure. TH4+ and 70% ethanol both significantly (P ≤ 0.05) affected larval development, with 58.8 and 85.8% reduction, respectively. Neither sodium hypochlorite nor phenol significantly affected larval development (2.8 and 21.0%, respectively). Sodium hypochlorite treatment caused a visible decortication of the eggshell; however, phenol-treated embryonated Toxascaris eggs appeared more or less morphologically normal. In conclusion, the disinfectants tested induced variable degrees of decortication and suppression of larval development. Virkon®S was the most effective disinfectant against Toxascaris eggs, suggesting that it is the most advisable one to use. To the best of our knowledge, this is the first report of the use of Virkon®S as an ovicide and/or larvicide of helminths, particularly Toxascaris leonina.

Fasciola hepatica infections in cattle and the freshwater snail Galba truncatula from Dakhla Oasis, Egypt.

Infection by Fasciola species was investigated in seven districts of Dakhla Oasis, Egypt, through abattoir inspection of cattle livers for adult worms and sedimentation of faecal samples from local cattle to detect Fasciola eggs. In addition, lymnaeid snails collected from the study area were examined microscopically for developmental stages of Fasciola spp. Abattoir inspection revealed that 51 out of 458 cattle livers (11.1%) contained adult flukes, which were identified morphologically as Fasciola hepatica. Examination of the cattle faecal samples revealed that 142 out of 503 (28.2%) contained Fasciola eggs. The collected snails, identified as Galba truncatula and Radix natalensis, showed larval stages of Fasciola in 71 out of 731 (9.7%) G. truncatula, while R. natalensis showed no infection. Specific duplex polymerase chain reaction (PCR) targeting the mitochondrial cox1 gene of F. hepatica and Fasciola gigantica was carried out on DNA extracted from pooled infected snails and adult worms. The F. hepatica size amplicon (1031 bp) was obtained from both the infected G. truncatula and the adult worms isolated from cattle livers from different districts. The amplicon sequences were identical to the published sequences of F. hepatica mitochondrial cox1 gene. In conclusion, the zoonotic importance of Fasciola infection and appropriate hygienic measures must be taken into consideration in Dakhla Oasis, Egypt.

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

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 » 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 » 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.

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

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 » 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 » 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 χ 2 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.

Distribution and characterization of canine Chagas disease in Texas.

Although acute and chronic cases of canine Chagas disease have been reported from multiple areas in the southern region of the United States, little data are available on current disease occurrence patterns in endemic areas. Therefore, a study to assess frequency, geographic distribution, signalment, and clinical spectrum of Chagas disease in domestic dogs from Texas was conducted. Serology, histopathology, and clinical case records from multiple institutions for the time period 1993-2007 were analyzed. A total of 537 serologically and/or histopathologically confirmed cases were documented. Cases were reported from 48 of 254 counties within Texas, covering all major geographic regions. Forty-eight dog breeds were represented among the cases, primarily in the sporting and working groups. In histopathologically confirmed cases, acute death occurred in 42%, approximately half of which were <1 year of age. Nearly all cases with histopathology data reported myocarditis (97.9%) and observation of Trypanosoma cruzi organisms (81.7%). Predominant clinical observations included enlarged heart, lethargy, anorexia, ascites, cardiac conduction disturbances, and respiratory difficulties. An increasing rate of serologic test submissions was noted over the study period, with an overall positive test prevalence of 20.3%. The study results provide strong evidence that an active canine Chagas disease transmission cycle is present throughout all ecoregions of Texas, affecting a broad range of dog breeds and age groups.

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)

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.

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.

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.

Experimental transmission of the Texas strain of Hepatozoon canis.

Nine dogs were fed Hepatozoon canis-exposed Rhipicephalus sanguineus ticks; 6 showed clinical signs suggestive of canine hepatozoonosis, and the parasite was found in sections of muscle tissue from 2 of the dogs. Schizont-like cysts were found in the skeletal muscle of both infected dogs as were gametocytes in the circulating leucocytes. Periosteal new-bone lesions were seen in 1 dog. Attempts to infect a raccoon, 3 cats, 6 laboratory mice, and tick- or canine-cells in vitro, failed.

Control of cyathostome infections in mares treated at parturition with ivermectin.

Six mares were treated on the day of parturition with an intramuscular injection of 0.2 mg kg-1 ivermectin and placed in a pasture free of equine parasites as soon as possible after foaling. The mares and their foals were compared with a similar group of untreated mares and foals on an adjoining pasture. The experimental data was derived from mare and foal fecal egg counts, foal necropsies and pasture larval counts. Ivermectin administered to mares on the day of parturition, when combined with movement to parasite-free pastures, significantly lowered the cyathostome (small strongyle) egg production for 4 months. This reduced cyathostome exposure was reflected in lower worm-burdens in their foals for 5 months. The results indicate that ivermectin will effectively control equine strongyles when mares and their foals are moved to parasite-free pastures.

Increased activity of bovine ADCC effector cells during acute Babesia bovis infection.

Mononuclear effector cells from the peripheral blood of Babesia bovis-infected cattle responded during initial infection and destroyed Fc-bearing target cells. The activity of these cells was measured in an antibody-dependent, cell-mediated cytotoxicity (ADCC) assay utilizing chicken erythrocytes coated with bovine anti-chicken erythrocyte antibody as targets. The activity of these effector cells was enhanced during the parasitemic crisis and returned to normal levels of activity following the resolution of parasitemia. This suggests that ADCC mechanisms may be involved in resolution of infection of cattle with B. bovis.

Hypocholesterolemia and hypocortisolemia in acute and terminal Babesia bovis infections.

Sera from Babesia bovis-infected cross-bred cows and purebred steers were evaluated throughout the course of acute Babesia bovis infection for cholesterol and cortisol concentrations. Cholesterol and cortisol values of surviving cattle became markedly reduced (less than 50% of normal values) during the acute phase of the disease, Days 10-15 postinoculation, and returned to essentially normal values by the end of the 35 day experimental period. The combined control group values were approximately 2.98 mM/l cholesterol and 0.085 mM/l cortisol throughout the experimental period. The results suggest that if normal synthesis of cholesterol by hepatocytes or other tissues is not maintained, then cholesterol-derived compounds such as cortisol may not be produced at levels adequate to protect against the effects of stress and cell damage during the disease process.

The role of specific immunoglobulins in antibody-dependent cell-mediated cytotoxicity assays during Babesia bovis infection.

A stabilate prepared from Babesia bovis-infected Boophilus microplus ticks was used to infect intact adult cattle. Whole sera and immunoglobulin fractions from representative sera were tested by complement fixation (CF), indirect fluorescent antibody (IFA), and antibody-dependent cell-mediated cytotoxicity (ADCC) assays. The last test utilized 51Cr-labeled chicken erythrocytes coated with Babesia bovis antigen as targets. Mononuclear cell preparations, obtained from peripheral blood of normal donors and consisting of lymphocytes with 2--6% large monocytes, were used as the source of effector cells. Antibody activity was detected by all tests between 14 and 16 days following infection. Specific IgM and IgG1 were reactive in both CF and IFA tests, although the development of high titers was attributable to IgG, alone. The ADCC activity was restricted to IgG1 fractions and was greater in those sera or fractions with greater CF activity. No activity was demonstrated in IgG2 fractions by any test used.

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.

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.

The bovine immune response to tick-derived Babesia bovis infection: serological studies of isolated immunoglobulins.

A cryopreserved stabilate was prepared from Babesia bovis-infected Boophilus microplus ticks. The stabilate was used to infect a group of mature Bos taurus-Bos indicus cows. The survivors of the initial infection were rechallenged with the homologous stabilate 65 days later. All cows reacted parasitologically after primary challenge, and most responded serologically. With the exception of two cows, those not responding serologically died of acute babesiosis. The two that survived the primary challenge, but did not produce detectable antibody, died after secondary challenge. All serologically-positive cows survived the secondary challenge. Complement fixation and indirect fluorescent antibody tests were performed on all cows' sera and, in addition, immunoglobulin fractions were prepared and analyzed from selected sera. Both IgM and IgGl were important in the initial response. A secondary IgM response was noted by complement fixation assays. No activity was detected in any IgG2 fraction.

Clinical and serological evidence of bovine babesiosis and anaplasmosis in St. Lucia.

One hundred fifty-nine Holstein calves were imported into St. Lucia from the U.S.A. An outbreak of babesiosis occurred 17 days post-arrival, and an outbreak of anaplasmosis occurred 5 months after importation. Sera obtained 3, 6, and 12 months post-importation revealed a high prevalence of IFA titres to Babesia bovis and B. Bigemina 3 months after arrival and an increase in titres to Anaplasma marginale 6 months after arrival. Sera obtained from native cattle from several places on the island indicated infection rates of 80, 65 and 64% with A. marginale, B. bigemina and B. bovis, respectively. The rapid card test only indicated a 25% prevalence of infection of native cattle by A. marginale. This low prevalence was probably due to deterioration of serological activity during shipment.

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.

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.