Infectivity and cross-immunity studies of Theileria lestoquardi and Theileria annulata in sheep and cattle: II. In vitro studies

In the studies previously reported, the tick-borne protozoan parasites Theileria lestoquardi and Theileria annulata were shown to differ in their capacity to infect sheep and cattle. In the studies presented here, these findings were further supported. In vitro infectivity of T. lestoquardi and T. annulata sporozoites for peripheral blood mononuclear cells of sheep and cattle were determined by analysis of cell cultures for cell proliferation, the detection of parasites in Giemsa-stained cytospin smears and the establishment of continuously growing schizont-infected cell lines. In the same way, the development of schizont-infected cells into continuously growing cell lines was studied with material isolated ex vivo from the sheep and cattle undergoing primary infections described elsewhere. Comparisons were also made between development of ex vivo cell lines from animals undergoing primary infections with those of the animals undergoing challenge infection with the other parasite species. Theileria species specific primers were used in a PCR to determine the identity of the parasites in the cell lines. These in vitro studies confirmed earlier observations that T. lestoquardi was unable to infect cattle, whereas infection of all sheep with T. annulata was proven. Moreover, earlier indications of the development of partial cross-immunity in sheep of T. annulata to T. lestoquardi and vice versa were strengthened. These findings may thus have consequences for the understanding of the epidemiology of T. lestoquardi infections of sheep. On the other hand. since piroplasms were not demonstrated in sheep infected with T. annulata, such sheep will not be infective to ticks and will consequently be unlikely to play a role in the maintenance and transmission of T. annulata to cattle.

Comparison between effects of standard feed and whole wheat supplemented diet on experimental Eimeria tenella and Eimeria maxima infections in broiler chickens

The effects of experimental infections with Eimeria tenella (Experiment 1, n = 144) or E. maxima (Experiment 2, n = 216) in broiler chickens fed whole wheat, with or without access to grit, as compared to a standard pelleted feed were studied. Inclusion of whole wheat was gradually increased up to 30% at 3 weeks of age. Grit was given separately. The chickens were kept on litter in a parasite-free environment with free access to water and feed. At 3 weeks of age half the number of chickens were individually inoculated with 500 sporulated oocysts of E. tenella (Experiment 1) or 3,000 sporulated oocysts of Eimeria maxima (Experiment 2), and the remaining birds were kept separate as uninfected controls. Neither coccidiostats nor growth enhancers were used. Oocyst concentration was determined from each group separately. Intestinal lesions were scored on 6 birds per feed regime 7 d postinoculation, and on the remaining birds at slaughter. Diet had no significant effect or bird performance during infection. However, there was an indication that the E. maxima infection had more negative effect on weight gain in birds given standard feed than in those given whole wheat supplement, but the difference was not significant (p < 0.09). The number of oocysts shed or mean intestinal lesion scores did not differ between diets in either experiment. In both experiments, the number of Clostridium perfringens was higher in the caeca of inoculated birds, but there were no differences between diets.

Sarcocystis dubeyi n. sp. (Protozoa: Sarcocystidae) in the water buffalo (Bubalus bubalis)

Sarcocystis dubeyi n. sp. is proposed for a species forming thick-walled, microscopic sarcocysts in striated muscular tissues of the water buffalo (Bubalus bubalis). Sarcocysts of S. dubeyi were found in histological sections of skeletal muscles and esophagus, but not in heart and tongue, of 8 (13%) of 60 water buffaloes examined in Ho Chi Minh City, Vietnam. Sarcocysts of S. dubeyi were up to 600 microns long and up to 200 microns wide. The cyst wall was 4.5-9 microns thick and was composed of tightly packed, cylindrical villar protrusions (Vp) that had a uniform width of up to 3 microns, a length of up to 8 microns, and a blunt, often flattened tip. The Vp contained microfilaments but no prominent electron-dense granules. The definitive host of S. dubeyi was not determined, but it could possibly be humans or other primates. By the present description, 4 Sarcocystis species are recognized in the water buffalo: the macrocyst-forming Sarcocystis fusiformis and S. buffalonis and the microcyst-forming S. levinei and S. dubeyi.

Effect of betaine supplement on broiler performance during an experimental coccidial infection

A trial was conducted to investigate the effects of betaine as a feed supplement, given singly and in combination with the ionophore coccidiostat narasin, on broiler performance during an experimental coccidial infection. Five hundred and sixty female Ross broiler chickens were kept in floor pens and given a wheat-based diet. At 10 d of age, 420 chickens were individually inoculated with a mixture of Swedish chicken Eimeria isolates containing E. acervtulina, E. praecox, E. maxima, and E. tenella. Remaining birds were kept as uninoculated controls. The effects of betaine (0 or 1.0 g/kg) and narasin (0 or 70 ppm) added to the basal diet were evaluated. Overall, betaine as a single feed supplement improved live weight by 5.7, 5.4, and 5.6% at 22, 29, and 36 d, respectively, but had no positive effect in combination with narasin. A longer withdrawal period of the coccidiostat (10 vs 5 d) did not affect live weight, but significantly increased feed intake by 9.6% and feed conversion ratio by 12.6%, irrespective of betaine supplement. Inoculated birds had a 10% lower live weight than uninoculated chickens. Performance of uninoculated birds was similar to that of inoculated birds treated with narasin, except at 7 d after inoculation, when live weights of uninoculated birds were significantly higher. Chickens given coccidiostat had less Clostridium perfringens in their ceca, but the prevalence was not altered by betaine supplement. There was no difference in intestinal lesion scores between inoculated chickens given coccidiostat or not, despite the better performance of chickens given coccidiostat. Betaine did not affect Eimeria oocyst output or intestinal lesion scores.

Comparison between a live, attenuated anticoccidial vaccine and an anticoccidial ionophore, on performance of broilers raised with or without a growth promoter, in an initially Eimeria-free environment

An experiment was carried out to study the effects of vaccination with Paracox, a live, attenuated vaccine against avian coccidiosis, on broilers isolated from extraneous Eimeria parasites. The study involved 3200 broiler chickens raised in floor pens similar to commercial conditions, but in an initially Eimeria-free environment. Forty percent of the chickens were vaccinated at 3 days of age and given either a basal unmedicated feed or a feed supplemented with the feed antibiotic virginiamycin. Unvaccinated birds were given either the basal feed or feed supplemented either with virginiamycin or the anticoccidial ionophore narasin. At slaughter at 36 days of age vaccinated birds had a lower live weight than non-vaccinated birds. The difference was 4.6% in unmedicated, and 6.0% in virginiamycin medicated chickens. Feed conversion ratio at slaughter was 2.5% higher for unmedicated vaccinated birds, and 1.3% higher for virginiamycin medicated vaccinated birds, compared to respective non-vaccinated groups. There was no significant difference in overall performance of unvaccinated birds given narasin as compared to virginiamycin. At 10 days post vaccination vaccinated birds had a higher number of Clostridium perfringens in the caeca, but there was no difference thereafter. Throughout the experiment, caecal clostridial counts were considerably higher in vaccinated unmedicated birds than in unvaccinated birds given narasin. The number of oocysts shed in the vaccinated groups was very low, but during a subsequent challenge with E. maxima and E. tenella the birds' immunity was found to be satisfactory.

A field survey on the distribution of strongyle infections of horses in Sweden and factors affecting faecal egg counts

Faecal egg counts were performed during the first quarter of 1995 on samples from 1183 horses of varying breeds, ages and gender on 110 farms in 3 regions of Sweden. The majority of the horses had been treated with ivermectin or pyrantel when stabled the previous autumn. The risk of reinfection with strongyles between treatment and sampling was therefore considered to be minimal. Consequently, the results reflect primarily the occurrence of worms originating from inhibited strongyle larvae refractory to anthelmintic treatment. A total of 922 (78%) individuals were found to shed strongyle eggs, and 15 (14%) of the farms studied had at least one horse infected with Strongylus vulgaris. There was a significant, gradual decrease in faecal egg output in horses originating from the southern to the northern part of Sweden. Horses from studfarms showed significantly higher numbers of strongyle eggs/g faeces (EPG) as compared to those on other types of farms, such as riding-schools and boarding stables. However, there was no correlation between herd size and mean herd EPG. The output of strongyle eggs was highest in horses aged 2 and 3 years. EPG values then declined with increasing age of the horse. Horses treated with ivermectin in the previous autumn showed significantly lower EPG values than untreated horses and those treated with pyrantel pamoate.

Sarcocystis species in skeletal muscle of otter (Lutra lutra)

Cysts of a Sarcocystis species were found in large numbers in skeletal muscle of an otter (Lutra lutra) which was raised in Norway and died in captivity in Sweden. This is the first report of Sarcocystis infection in the otter. The sarcocysts were 0.3-2.3 mm long and 0.06-0.25 mm wide. As judged by light microscopy the sarcocyst walls were thin (< 3 microns) with a serrated surface but without visible projections. By transmission electron microscopy, the sarcocyst wall measured 0.6-1.8 microns and had minute undulations covering the entire sarcocyst surface giving the wall a wavy appearance. Septa were indistinct. The sarcocysts contained few metrocytes and numerous bradyzoites. Sarcocysts were not found in 69 other otters subjected to necropsy in Sweden.

An IgG avidity ELISA to discriminate between recent and chronic Neospora caninum infection

The avidity of IgG antibodies directed to Neospora caninum was measured using an IgG avidity enzyme-linked immunosorbent assay (ELISA) employing N. caninum proteins incorporated into immunostimulating complexes as antigen. In this ELISA, low-affinity antibodies were eluted by adding an incubation step with urea after the serum incubation. The antibody titers obtained with and without incubation with urea were then used to calculate the IgG avidity values. Analysis of sequential sera collected from experimentally infected calves revealed that the avidity increased during the course of infection. Three weeks after infection, the IgG avidity was 9-18%, and 24 weeks later it had increased to 58-76%. Cattle naturally infected for more than 6 months all had avidities >50%. The results in this study, however preliminary, indicate that the IgG avidity ELISA can be used to discriminate between recent and chronic N. caninum infections and may therefore be a valuable complement to IgG assays in epidemiologic studies of N. caninum infection in cattle.

Effects of temperature and humidity on oviposition, molting, and longevity of Dermanyssus gallinae (Acari: Dermanyssidae)

The juvenile development and survival of Dermanyssus gallinae (De Geer) kept in vitro at different temperatures and humidity were investigated to obtain biological baseline data for a Swedish population. Individual females, eggs, larvae, and protonymphs were observed with regard to egg production, duration of various stages, and longevity when kept at different temperatures and relative humidities. Female mites laid eggs at temperatures between 5 and 45 degrees C with the highest numbers laid at 20 degrees C and 70% RH, but development to larvae and protonymphs was only observed at temperatures ranging from 20 to 25 degrees C. The average duration of oviposition varied from 1.0 to 3.2 d within the temperature range 20-45 degrees C but was gradually increased to 28 d at 5 degrees C. Specimens survived for up to 9 mo without access to food when kept in the temperature range of 5-25 degrees C. Temperatures > 45 degrees C and at -20 degrees C were found to be lethal. Longevity was similar for females and protonymphs kept at 30 and 45% RH, but it was enhanced at 70 and 90% RH for protonymphs. This study showed that D. gallinae can survive for a long time without feeding if the microclimate is suitable, but it does not thrive at low relative humidities and at temperature extremes. This indicates that changing of the abiotic conditions in infested poultry houses could be a possible measure to reduce mite populations.

Neospora caninum infection and repeated abortions in humans

To determine whether Neospora caninum, a parasite known to cause repeated abortions and stillbirths in cattle, also causes repeated abortions in humans, we retrospectively examined serum samples of 76 women with a history of abortions for evidence of N. caninum infection. No antibodies to the parasite were detected by enzyme-linked immunosorbent assay, immunofluorescence assay, or Western blot.

Oral Neospora caninum inoculation of neonatal calves

Four calves born to cows seronegative for Neospora caninum were dosed orally within 6 h after birth with tachyzoites of the bovine N. caninum Nc-SweB1 isolate added to colostrum. Two of the calves were dosed via stomach tube and two by feeding bottle. The latter two calves showed transient fever and passed blood-stained diarrhoea 1-2 weeks after inoculation. From 5 weeks after inoculation they developed a significant antibody response which remained high until the calves were euthanised and necropsied at 15 and 19 weeks after inoculation, respectively. The two calves inoculated by stomach tube showed no clinical signs and they remained seronegative throughout the study. At necropsy of the seropositive calves, no pathological lesions were seen, and parasites were not detected by immunohistochemistry. Neospora caninum was not re-isolated in cell culture from the brains of the seropositive calves; however, N. caninum DNA was detected in brain from both of them by PCR. The data suggest that oral infection of N. caninum via colostrum might be a possible route of vertical transmission in newborn calves, in addition to transplacental infection.

Detection of antibodies to Neospora caninum in bovine postabortion blood samples from Hungary

In order to obtain data on the occurrence of the protozoan parasite Neospora caninum as a potential factor in the aetiology of reproduction problems in cattle, 97 postabortion sera were examined by ISCOM ELISA and IFAT for the presence of antibodies in N. caninum. The results showed 10% and 9% seropositivity by the ELISA and IFAT, respectively. In 2 of the 10 seropositive cases no other fetopathogenic agents (such as Chlamydia sp., Leptospira spp. or bovine viral diarrhoea virus) were detected. These data confirm the presence of N. caninum in cattle in Hungary.

Experimental infection of dogs with the nasal mite Pneumonyssoides caninum

A successful experimental transmission of the canine nasal mite, Pneumonyssoides caninum, is described. Some 11 weeks after repeated systemic ivermectin treatment, four Beagles were inoculated via the right nostril with 20 P. caninum mites of different sexes and life stages, obtained at the necropsy of an infected dog. The inoculated dogs and a matching uninoculated control were observed for clinical signs for 14 weeks and then euthanised. Vague upper respiratory signs and a transient minor increase in the number of eosinophils in peripheral blood were recorded in the inoculated dogs. At necropsy 4-12 P. caninum mites were found in the nasal cavities and sinuses of the inoculated dogs, but none in the control. In three out of the four infected dogs mites were found in both the right and left nasal cavities and sinuses of the skull. Since in no case more mites than the number used for inoculation were detected it is not clear if the mites managed to reproduce in the dogs. Inflammatory lesions were seen most consistently in the olfactory mucosa, respiratory mucosa and tonsils, and growth of opportunistic bacteria was observed in the tonsils of the infected dogs. The inflammatory lesions seen in the olfactory mucosa may explain why dogs infected with P. caninum sometimes appear to suffer from impaired scenting ability.

Experimental porcine neosporosis

Six gilts were inoculated intramuscularly with 2.5x10(6) tachyzoites of Neospora caninum on three different days of gestation to study the pathogenic effect of Neospora infection in pigs, including possible transplacental transmission. The gilts were euthanized 59, 30, and 9/10 days postinoculation (p.i.), corresponding to days 107, 102/106 and 110/111 of pregnancy. With the exception of one animal (euthanized day 9 p.i.) all gilts seroconverted as measured by the indirect, fluorescent antibody test (IFAT). Neosporosis with multifocal intralobular necrotizing hepatitis was seen in the two gilts inoculated 9/10 days before euthanasia. The uterus of one gilt inoculated 59 days before euthanasia revealed granulomatous and focal necrotizing endometritis with a corresponding multifocal necrosis of the trophoblasts of two fetuses. Transplacental neosporosis was indicated in the two fetuses by strongly elevated Neospora IFAT titres in pleural fluid and by the presence of multifocal necrotizing encephalitis and hepatitis together with non-suppurative myocarditis, pneumonitis, nephritis and hepatitis. Furthermore, N. caninum was re-isolated in cell culture from one of these fetuses. A third fetus from the same gilt revealed only disseminated, pinpoint necroses in the liver. Immunohistochemically, N. caninum tachyzoites were detected in association with histopathological changes in the liver and the endometrium of the gilts, and in the brain, liver, and allantochorion of the three fetuses.

Epidemiology of Anoplocephala perfoliata infection in foals on a stud farm in south-western Sweden

The egg output and humoral antibody response to scolex antigens of the equine tapeworm Anoplocephala perfoliata were monitored in naturally infected foals by an egg flotation/centrifugation method and an indirect enzyme-linked immunosorbent assay (ELISA). The study was performed on a stud farm in south-western Sweden between May 1994 and April 1995. Sequential blood and faecal samples were taken from 21 foals during their first summer on pasture and until tapeworm eggs were detected. Results were expressed separately for 10 and 11 foals born before and after the end of April 1994, respectively. Increased levels of antibodies were noticed from October and onwards in both groups whereas tapeworm eggs were detected in the faeces of all foals about 4 months later. The antibody response was similar in both groups but it was more pronounced in foals born before April 1994. All foals were treated in March 1995 with an oral paste formulation of pyrantel pamoate at a dose rate of 38 mg/kg bodyweight. Most animals responded to the anthelmintic treatment and one month later, tapeworm eggs were only detected in one out of the 18 foals examined one month after treatment. Thus, the treatment reduced the number of A. perfoliata egg positive horses by 94%. A concomitant decline in antibody levels was also observed. Western immunoblot analysis of sequential individual serum samples showed that at least 10 different scolex antigens in the molecular weight range 10-200 kDa were recognised. Banding intensities, especially of the 10 kDa, 45 kDa and 66 kDa proteins were different in the sequential sera taken during the course of infection.

Prevalence of antibodies to Neospora caninum and Toxoplasma gondii in cattle and water buffaloes in southern Vietnam

Serum samples from 200 dairy cattle and 200 beef water buffaloes were collected in southern Vietnam during May to September 1995. The sera were analysed for antibodies to Neospora caninum by an enzyme-linked immunosorbent assay and the indirect fluorescent antibody test, and for antibodies to Toxoplasma gondii by the direct agglutination test. Significant levels of N. caninum antibodies were detected in 5.5% of the cattle sera and in 1.5% of the water buffalo sera. 10.5% of the cattle sera and 3% of the water buffalo sera were found to contain T. gondii antibodies. Two of the cattle sera had both T. gondii and N. caninum antibodies. The present communication is the first to report serological evidence of N. caninum infection in the water buffalo.

Comparison between effects of standard feed and whole wheat supplemented diet on experimental Eimeria tenella and Eimeria maxima infections in broiler chickens

The effects of experimental infections with Eimeria tenella (Experiment 1, n = 144) or E. maxima (Experiment 2, n = 216) in broiler chickens fed whole wheat, with or without access to grit, as compared to a standard pelleted feed were studied. Inclusion of whole wheat was gradually increased up to 30% at 3 weeks of age. Grit was given separately. The chickens were kept on litter in a parasite-free environment with free access to water and feed. At 3 weeks of age half the number of chickens were individually inoculated with 500 sporulated oocysts of E. tenella (Experiment 1) or 3,000 sporulated oocysts of Eimeria maxima (Experiment 2), and the remaining birds were kept separate as uninfected controls. Neither coccidiostats nor growth enhancers were used. Oocyst concentration was determined from each group separately. Intestinal lesions were scored on 6 birds per feed regime 7 d postinoculation, and on the remaining birds at slaughter. Diet had no significant effect or bird performance during infection. However, there was an indication that the E. maxima infection had more negative effect on weight gain in birds given standard feed than in those given whole wheat supplement, but the difference was not significant (p < 0.09). The number of oocysts shed or mean intestinal lesion scores did not differ between diets in either experiment. In both experiments, the number of Clostridium perfringens was higher in the caeca of inoculated birds, but there were no differences between diets.

Redescription of Sarcocystis levinei Dissanaike and Kan, 1978 (Protozoa: Sarcocystidae) of the water buffalo (Bubalus bubalis)

Sarcocystis levinei Dissanaike and Kan, 1978, is redescribed because the original description was a mixture of 2 species, the amended S. levinei and the newly recognized S. buffalonis Huong, Dubey, Nikkilä, and Uggla, 1997. In histological sections, S. levinei sarcocysts are microscopic, up to 640 microm long and up to 95 microm wide. Ultrastructurally, the cyst wall is thin (< 1.0 microm thick) with a minute undulating surface and smooth, hairlike villar protrusions arising at irregular distances from the cyst wall. The villar protrusions have a dome-shaped base (approximately 0.5 microm thick), a fingerlike middle part, and a tapering distal end (<0.1 microm thick). The morphological features of the sarcocyst resemble those of S. cruzi (Hasselman, 1926) Wenyon, 1926, of cattle. Sarcocystis levinei sarcocysts were found in striated muscles including heart, esophagus, tongue, and skeletal muscle. The buffalo myocardium is parasitized exclusively by S. levinei, whereas >1 Sarcocystis species may occur concurrently in other muscular tissues of water buffaloes. Two dogs, but not 2 cats, fed water buffalo hearts infected with S. levinei sarcocysts shed sporocysts measuring 9.5-10.5 x 14.0-16.5 microm starting from days 16 and 18, respectively.

Antibody responses of cows during an outbreak of neosporosis evaluated by indirect fluorescent antibody test and different enzyme-linked immunosorbent assays

Serum samples from 70 (33 aborting and 37 non-aborting) dairy cows from a herd in California were analyzed for Neospora caninum antibodies in different laboratories by various serologic assays including enzyme-linked immunosorbent assay (ELISA) with recombinant antigens (Nc4.1 and Nc14.1), kinetic ELISA, whole tachyzoite lysate ELISA, immunostimulating complex (iscom) ELISA, antigen capture competitive inhibition ELISA, and by the indirect fluorescent antibody test. Eighteen percent of pregnant cows in this herd had aborted within 2 mo of the index case. All 70 cows had antibodies to N. caninum by at least 1 of the tests. Antibody levels to N. caninum in aborting cows as a group were higher than in nonaborting cows. However, it was concluded that no serological test could be used to establish definitively that N. caninum caused the abortion in an individual cow.

Toxoplasma gondii infection in the mountain hare (Lepus timidus) and domestic rabbit (Oryctolagus cuniculus). I. Pathology

Mountain hares and domestic rabbits infected experimentally with Toxoplasma gondii were compared in respect of pathological changes and distribution of organisms in the tissues. Seven hares and nine rabbits were each inoculated orally with 50 oocysts of the T. gondii Tg-SweF1 isolate and killed after one week to avoid adverse clinical effects. The only clinical sign observed was respiratory distress in a single hare. At necropsy, gross lesions, which occurred only in the hares, were found in the mesenteric lymph nodes and occasionally the liver. Histologically, the hares showed extensive necrotic areas in the small intestine, mesenteric lymph nodes and liver, and less prominent foci of necrosis in various other organs. Immunohistochemically, T. gondii was identified in all organs examined, large numbers of organisms being associated with the lesions. These findings were analogous to those seen previously in naturally infected hares. In the rabbit, the pathological changes consisted mainly of accumulations of mononuclear cells in the liver and heart, and T. gondii was found only in the heart and skeletal muscle of two rabbits. Thus, the hares developed severe acute toxoplasmosis, but the rabbits showed few organisms and no major tissue damage one week after inoculation.

Toxoplasma gondii infection in the mountain hare (Lepus timidus) and domestic rabbit (Oryctolagus cuniculus). II. Early immune reactions

As already reported, the mountain hare is much more susceptible than the domestic rabbit to oral inoculation with Toxoplasma gondii, as judged by pathological changes and dissemination of parasites within the body. In the present paper, further interspecies variations are reported. Concentrations of the acute phase reactant haptoglobin were raised in hares but not in rabbits one week post-infection (pi), probably reflecting the severe tissue damage present. No difference in the early humoral immune response of hares and rabbits was found, both species producing IgM and IgG antibodies to T. gondii one week pi. Lymphocyte stimulation tests performed before and one week after inoculation showed a high proliferative response to the parasite in blood cell cultures from rabbits but not hares. The fatal outcome of T. gondii infection in the hares is probably due, at least in part, to the lack of cellular response.

Occurrence of Gasterophilus intestinalis and some parasitic nematodes of horses in Sweden

A survey was performed on the occurrence of some internal parasites in 461 horses (1-30 years old) slaughtered from October 1992 to September 1993 at the Linköping abattoir in central Sweden. Macroscopical examination was carried out specifically for parasites of the tear ducts and conjunctival sacs of the eyes, and of selected parts of the alimentary tract and cardio-vascular system. The following parasites were found in selected parts of the large intestine: encapsulated cyathostome larvae (in 35.6% of the horses), and mature strongyle worms (17.4%); in the stomach: Gasterophilus intestinalis (12.3% during October-June) and Habronema muscae (1.1%); and in the conjunctival sac: Thelazia lacrymalis (3.1%). Significantly more encapsulated cyathostome larvae were found during January to June than during other times of the year, and horses aged 1-5 years harboured significantly more larvae than older horses. Severe damage to the cranial mesenteric artery and its main branches was noticed in 16 (6.1%) out of 263 horses specifically examined. However, the 4th stage larva of Strongylus vulgaris was only recovered in 6 (2.3%) of the horses. Quantitative and qualitative faecal egg counts were done on 412 and 384 of the horses, respectively. Eggs of strongyles, Parascaris equorum and Strongyloides westeri were found in 78.1%, 1.9% and 0.2% of the faecal samples, respectively. Highest prevalence of strongyle eggs was found during July to September. Third stage larvae of the following nematodes were recovered from faecal cultures: subfamily Cyathostomum sensu lato (78.1%) Triodontophorus spp. (6.5%), Strongylus vulgaris (3.6%), Trichostrongylus axei (1.3%), while Gyalocephalus sp., Oesophagodontus sp., Poteriostomum sp. and Strongylus edentatus each comprised less than 0.5%.