Studies on the parasites of zebras. V. Nematodes of the Burchell's and Hartmann's mountain zebras from the Etosha National Park, South West Africa/Namibia

Nine Burchell's and 6 Hartman's mountain zebras were culled during the 3 climatic periods characteristic of the Etosha National Park, South West Africa/Namibia, and were examined for helminths. The Burchell's zebras ranged in age from 4 1/2 to 19 years and the mountain zebras from 3 1/2 to 13 years. Twenty-five species of nematodes, belonging to the families Atractidae, Strongylidae, Oxyuridae, Onchocercidae and Habronematidae, were recovered. Of the family Cyathostominae, the following species were the most numerous in the Burchell's zebras: Cyathostomum montgomeryi (7 120-67 042), Cylicocyclus triramosus (11-34 540), Cylicostephanus minutus (4 698-40 019) and Cylindropharynx sp. (? intermedia) (3 591-40 018). The atractids present were: Crossocephalus viviparus (20-5 045 212) and Probstmayria vivipara (5 140-3 801 300). Three of the above cyathostome species were also most abundant in mountain zebras: Cylicocyclus triramosus (54-19 782), Cylicostephanus minutus (555-12 396) and Cylindrophrynx sp. (? intermedia) (3-5 325). New reports include Cylicostephanus longiconus in the Burchell's zebras and Cyathostomum alveatum, Cyathostomum montgomeryi, Cylicostephanus bidentatus and Draschia megastoma in the mountain zebra. The overwintering of 4th stage cyathostomes in the gut walls and their emergence which differ in the 2 hosts, are discussed.     

Studies on the parasites of zebras. IV. Cylicodontophorus reineckei n.sp. (Nematoda: Strongylidae) from the Burchell's zebra, Equus burchelli antiquorum H. Smith, 1841 and the mountain zebra, Equus zebra hartmannae Matschie, 1898

A new species of nematode, Cylicodontophorus reineckei, was collected from Burchell's zebra, Equus burchelli antiquorum H. Smith, 1841, in both the Etosha National and Kruger National Parks and from mountain zebra, Equus zebra hartmannae Matschie, 1898, in the Namib Naukluft Park in South West Africa/Namibia. These nematodes have an external leaf-crown with longer elements than those of the internal leaf-crown and a well-developed dorsal gutter. The very well-developed oesophageal funnel is both wider and deeper than the buccal capsule.     

Seasonal fluctuations of gastrointestinal helminths of camels in Kuwait

Over a period of 1 year, from May 1982 to April 1983, the gastrointestinal tracts of 240 camels were examined for the presence of parasitic helminths. The study quantifies the prevalence of gastrointestinal helminths and the seasonal fluctuations in intestinal worm burdens and faecal worm egg counts. Among the three species of cestodes and eight species of nematodes which were recorded for the first time from Kuwait, Trichostrongylus probolurus (93.8%), T. colubriformis (34.2%) and Stilesia vittata (30.0%) were the most prevalent in the small intestine and Camelostrongylus mentulatus (59.6%) in the abomasum. Estimation of the intestinal worm burdens and faecal worm egg counts showed that Trichostrongylus infections were by far the most predominant. The highest worm and egg counts were recorded in June and August, during the hot dry season. This rise is attributed to infections acquired from February to April, during the cool wet season. Possibly the most effective control can be achieved by a critical treatment at the end of the wet season coinciding with the first rise in nematode population.     

Prevalence and intensity of intestinal helminths found in free-ranging golden lion tamarins (Leontopithecus rosalia, Primates, Callitrichidae) from Brazilian Atlantic forest

Helminth identification and egg counts were performed in 316 fecal samples during 4 years in 199 golden lion tamarins (GLTs), Leontopithecus rosalia, from two Brazilian conservation units. Tamarin sex and age, area of occurrence and helminth co-infection were tested as potential factors that could affect helminth prevalence and egg shedding in host individuals. Three nematodes species were found at low prevalences but not in both conservation units: Ancylostomatidae (12%), Ascarididae (1%) and Tripanoxyuris minutus, an Oxyuridae (4%). Three other species had high prevalences and were found in both conservation units: one acanthocephalan, Oncicola sp. (30%), and two nematodes, Spiruridae (24%), and Trichostrongylidae (31%). These three latter helminths had distinct prevalences between the conservation units, probably due to differences in availability of helminth infective stages in each area. Prevalences were greater in females for all helminth species; this was especially the case for Oncicola sp. Sex and age differences in helminth prevalence may be associated with changes in sexual steroid levels that accompany age and reproductive status. Frequency of simultaneous infections by the two helminths considered most pathogenic (Oncicola and Trichostrongylidae) were statistically lower than expected; this may be related to: (i) higher tamarin death rate caused by the association; (ii) differences in exposure to helminth infective stages in the various areas of occurrence; (iii) and competition between these helminth species. All helminth species followed a negative binomial distribution, with stronger clumping occurring in Trichostrongylidae and in female GLTs. Distinct transmission strategies of Oncicola sp. and Spiruridae, in contrast with Trichostrongylidae, may partially explain the different clumping levels of these helminths in GLTs. Mean fecal egg counts of all helminths were not different between GLT sexes, ages or areas of occurrence. The three most common helminth species may be a threat to isolated or dense GLT populations.     

A survey of helminth parasites of cats from Saskatoon.

In a survey of 52 cats from the Saskatoon area, Ollulanus tricuspis were found in 2 animals with burdens of 2308 and 533, respectively. Small burdens of the following helminths were also found: Physaloptera spp., Toxocara cati, Taenia spp., Dipylidium caninum, and Ancylostoma sp.     

Parasites of domestic and wild animals in South Africa. X. Helminths in impala

Two to four impala in the Nylsvley Nature Reserve were culled each month from February 1975-February 1976. Two trematode species, 1 cestode species and 13 species of nematodes were recovered from these antelope. Of these, Fasciola gigantica, Gongylonema pulchrum, Haemonchus placei and Trichostrongylus falculatus are new records for impala. In general, H. placei, Longistrongylus sabie and Impalaia tuberculata exhibited a similar pattern of seasonal occurrence. Adult worms were present during November-February, while marked inhibition in the development of large numbers of 4th stage larvae occurred from April-September or October. Cooperia hungi, Cooperioides hamiltoni and Cooperloides hepaticae followed a similar pattern, but inhibition in the 4th larval stage was not as marked and lasted from June-September. No seasonal pattern of prevalence could be determined for Trichostrongylus spp. The worm burdens of young impala increased with the age of the animals and reached a peak when the impala were 1 year old.     

Arthropod parasites of Hartmann's mountain zebra, Equus zebra hartmannae, in South West Africa/Namibia

Twelve Hartmann's mountain zebra, Equus zebra hartmannae, were shot for arthropod parasite recovery during the period June 1980-June 1981 on a farm in the Khomas Hochland region of South West Africa/Namibia. Four species of Gasterophilus larvae, 1 species of Rhinoestrus larvae and 3 ixodid tick species were recovered. The seasonal prevalence of the Gasterophilus species larvae and of Rhipicephalus evertsi mimeticus was determined. Three horses examined on the same farm were infested with larvae of 2 Gasterophilus species and with the same ixodid tick species as the zebras.     

Parasitic helminths in the digestive tract of six species of owls (Strigiformes) in Spain

A survey was carried out in Catalonia, Spain to determine the prevalence of parasitic helminths infesting the digestive tract of nocturnal raptors (Strigiformes). One hundred birds belonging to six owl species were examined. The number of birds examined ranged between three and 30. The overall level of infestation was 65% and the most frequent helminths present were nematodes, followed by trematodes, cestodes and acanthocephalans. Strigiformes showing the highest levels of infestation were little owls (Athene noctua), 86.7% of which were infested. Helminths with the highest prevalence were Synhimantus spp., intestinal capillarids, Brachylaima spp., cestodes and Centrorhynchus aluconis.     

Efficacy of a topical formulation of ivermectin against naturally acquired gastro-intestinal nematodes in weaner cattle

The efficacy of a topical formulation of ivermectin against naturally acquired gastro-intestinal nematodes in weaner cattle was evaluated. At slaughter, 14-15 days after treatment, burdens of Ostertagia spp, Trichostrongylus axei and Oesophagostomum radiatum were significantly lower in the treated calves than in the untreated controls (p<0.01). Efficacies (based on geometric mean worm burdens of treated and control groups) were 99.6%, 95.1% and 100% respectively. The sizes of the Cooperia spp and Trichuris ovis burdens in the treated group did not differ significantly at the 5% level of confidence from those in the control group.     

Parasites of South African wildlife. XII. Helminths of Nyala, Tragelaphus angasii, in Natal.

The helminths of 77 nyala, Tragelaphus angasii, from 4 game reserves in Natal, were collected, counted and identified. Ten nematode species and 4 nematode genera, a trematode species and paramphistomes, and 2 cestode genera were recovered from the antelope. Of these, a Cooperia rotundispiculum race, Gaigeria pachyscelis, a Gongylonema sp., Haemonchus vegliai, Impalaia tuberculata, an Oesophagostomum sp., a Setaria sp., Trichostrongylus deflexus, Trichostrongylus falculatus, the larval stage of a Taenia sp., a Thysaniezia sp. and Schistosoma mattheei are new parasite records for this host. Individual nematode helminth burdens varied from 3 to 13 493 and the total mean nematode burden was 700. The mean burdens of nyala from Mkuzi were the largest and those from animals from the Umfolozi Game Reserve and the False Bay Park the smallest. Ostertagia harrisi was the most prevalent nematode, and it was also the most numerous in nyala from Umfolozi, Mkuzi and False Bay. A race of Cooperia rotundispiculum was the most numerous in nyala from Ndumu. No clear-cut trends in the seasonal abundance could be discerned for any of the worm species recovered in this study.     

Parasites of South African wildlife. III. Helminths of common reedbuck, Redunca arundinum, in Natal

Twenty-six common reedbuck, Redunca arundinum, were shot in pairs at monthly intervals for 13 consecutive months in the Himeville region of Natal. Ten nematode species, 2 cestodes and 1 trematode were recovered from these animals. Cooperia yoshidai was both the most numerous and most prevalent worm and peak burdens occurred during summer. Thirty-one reedbuck, killed at different intervals in various localities within the St. Lucia Reserve, harboured between 4 and 11 nematode species, 1 cestode and 1 trematode. With the exception of 4 reedbuck shot during January 1987, in which Haemonchus contortus was the most abundant worm, C. yoshidai was again both the most abundant and most prevalent worm. Peak burdens of this nematode occurred during autumn to spring. The helminths of 5 impala, Aepyceros melampus, also shot in the St. Lucia Reserve were examined. Some of the worm species of impala were also found in the reedbuck from the same locality and the helminths of the 2 antelope species are compared. An amended list, which includes several new records of the parasites of common reedbuck in South Africa is provided.     

Dynamics of Ostertagia spp. and Cooperia oncophora in field-grazed cattle from weaning to 2 years old in New Zealand, with particular reference to arrested development

Gastrointestinal nematode parasite burdens were monitored in a herd of field-grazed cattle from weaning to 2 years old to allow observations to be made on the dynamics of burdens of arrested Ostertagia spp. and Cooperia oncophora. Arrested Ostertagia spp. accumulated in the herd over their first autumn and winter to reach a peak in late winter/spring (August-October). From October until late January they declined at a rate comparable to that at which they had accumulated. Numbers continued to decline at a slower rate until the following autumn (May) when they began to increase again. Observations on the decline of worm burdens in a group of animals which had been moved from pasture to worm-free conditions in October indicated that intake of infective larvae over late spring/summer contributed little to the number of arrested Ostertagia spp. in the herd. No clinical Type II ostertagiosis was observed in the field-grazed animals over the time of decline of the arrested worm burden, nor was there an increase in the number of adult Ostertagia spp. present. However, two of the animals removed from pasture to worm-free conditions developed Type II ostertagiosis approximately a month after the move. Worm burdens of successive groups of "tracers" grazed with the herd every 2 months indicated that there was a small seasonal increase in the propensity of Ostertagia spp. for arrested development. However, estimated accumulation rates of arrested larvae calculated from tracer worm burdens, suggest that this seasonal increase in propensity was not adequate in itself to account for the accumulation rate observed in "resident" animals of the herd. No comparable accumulation of arrested C. oncophora took place in resident animals over the first autumn and winter of the trial despite the fact that tracer worm burdens over this period indicated a marked seasonal increase in the propensity for arrested development by this species.     

The epidemiology of nematode and fluke infections in cattle in the Red River Delta in Vietnam

Over a period of 13 months, faecal samples were collected monthly from approximately 45 cattle over 3 months of age. Additionally, 74 calves of 1-2 months were sampled to determine the presence of Toxocara vitulorum eggs. Individual egg counts and infective strongyle larvae from pooled faecal samples were examined. Post-mortem worm counts were carried out on six groups of tracer calves (n=12) that had been kept for 4 weeks on pasture in and around the village studied. The following helminths were identified: T. vitulorum, Cooperia punctata, C. pectinata, C. oncophora, Oesophagostomum radiatum, Trichostrongylus axei, T. colubriformis, Haemonchus spp., Fasciola spp. and Paramphistomum spp. In 8% of the samples collected from young calves, individual egg counts for T. vitulorum were found indicative for pathogenic worm burdens. Strongyle egg counts and worm counts indicated that transmission is low without a distinct seasonality. In animals of 3-9 months old, a strongyle egg count peak can be demonstrated which at a higher age steadily and significantly decreased. In faecal cultures Cooperia spp. were most prominent in all age groups throughout the year with the exception of the period September-November when Haemonchus spp. and Oesophagostomum spp. were most prevalent. Fasciola spp. eggs were found in 22% of the collected faecal samples and the egg counts were low indicating that the intensity of Fasciola spp. infection is mild. Based on the present data, regular anthelmintic treatments seem not to be justified, except for a single treatment at the age of 2 weeks against toxocariosis.     

Relationship between helminth species diversity, intensity of infection and breeding management in dairy goats

Helminth infection, species diversity (proportion of each species in the community), species number, intensity of infection and anthelmintic resistance were investigated in 16 dairy-goat farms of south-western France. The aim of the study was to estimate which breeding management factors may affect diversity and intensity of infection. Anthelmintic resistance was investigated because this factor may modify composition of nematode communities. Farm history and breeding management were recorded by means of a questionnaire. Natural and experimental infections were compared to determine which strategy was the best to estimate diversity index and number of species from nematode community of a whole herd. A total of 17 species of helminths, among which 14 nematodes, one cestode (Moniezia spp.) and two trematodes (Paramphistomum daubneyi and Dicrocoelium lanceolatum) were recovered in the 26 necropsied culled goats. One culled goat worm burden represented conveniently species number but not species diversity (Shannon index) of parasite community harboured in the whole herd. Experimental sheep infection with larvae from pooled faeces of 15 goats was the best strategy to estimate species diversity in farms. Diversity could be predicted from the number of farms from which goats originated at constitution of the herd, the duration of goat winter withdrawal from pastures, and intensity of infection. Anthelmintic resistance was correlated with the number of farms of origin, area of permanent pastures and intensity of infection. The strategy adopted for the herd constitution was a critical step as species diversity and risk of anthelmintic resistance increased with the number of farms of origin. Intensity of infection was negatively correlated with species diversity. This suggested that more diverse communities were better controlled by the host, in agreement with the widespread statement that diversity would beget stability.     

SEASONAL CHANGES IN THE STRUCTURE OF NEMATODE POPULATIONS OF CATTLE IN NEW SOUTH WALES IN RELATION TO INHIBITED LARVAL DEVELOPMENT

Pasture plots in 3 climatic regions were contaminated with worm eggs of Ostertagia ostertagi, Trichostrongylus axel, Haemonchus spp and Cooperia spp in the autumn, winter and spring. Successive pairs of parasite-free calves were grazed on the plots for 7 to 10 days at 4-week intervals and then killed for worm counts 14 days after their removal from pasture.
On the Northern Tablelands of New South Wales, irrespective of the season of pasture contamination, the degree of inhibition of O. ostertagi was low in winter and highest in spring. T. axei showed similar trends while Cooperia spp showed negligible inhibition.
On the North Coast of New South Wales, inhibited larvae accounted for a very small proportion of the O. ostertagi burdens, while in comparison T. axei showed a much greater degree of inhibition. Larval inhibition of Haemonchus spp occurred in autumn and early winter after which it did not occur. There was negligible inhibition in Cooperia spp.
On the Central Coast of New South Wales, there was little inhibition of O. ostertagi and none in T. axel . For Haemonchus spp, inhibited larvae were found mainly in autumn and winter. The numbers of inhibited Cooperia larvae were also highest in autumn and winter and were associated with large worm burdens.
The marked difference between the tablelands and coastal regions in the seasonal trends of inhibition of O. ostertagi was considered to be due to a difference in strains between the geographical regions. The possible effect of climatic factors on the inhibition-proneness of infective larvae on pasture is discussed for Ostertagia and other nematodes. The roles of host resistance and density-dependence are also discussed.     

Use of moxidectin treatment in the investigation of abomasal nematodiasis in wild reindeer (Rangifer tarandus platyrhynchus)

An experiment was conducted to evaluate moxidectin as a tool for understanding the impact of parasitism on wild Svalbard reindeer (Rangifer tarandus platyrhynchus). Adult females were injected subcutaneously with moxidectin at a dose rate of 0-4 mg/kg bodyweight, and groups of animals were culled within its expected period of efficacy (around 14 days) or around 12 or 24 weeks after treatment. Moxidectin was effective in eliminating the reindeers' abomasal worm burdens, and although they became reinfected, worm burdens were significantly lower in the treated animals compared to the untreated controls for up to 24 weeks after treatment. Nematode eggs did not reappear in faeces until five weeks after treatment, a similar period to that claimed by the manufacturer for sheep and cattle. Animals culled 12 and 24 weeks after treatment had been reinfected and harboured a wide range of abomasal worm burdens which contributed to the understanding of the seasonal variation in the relationship between faecal egg count and worm burden.     

Parasites of domestic and wild animals in South Africa. XX. Arthropod parasites of the Cape mountain zebra (Equus zebra zebra)

The arthropod parasite burdens of 14 Cape mountain zebra (Equus zebra zebra), shot for survey purposes in the Mountain Zebra National Park in the eastern Cape Province, were determined. Three species of Gasterophilus larvae and 9 ixodid tick species were recovered. Larvae of Gasterophilus pecorum were the most numerous of the fly larvae recovered and Margaropus winthemi was the most abundant tick. Two horses examined in the park were infested with 3 species of Gasterophilus larvae and 7 species of ixodid ticks.     

Parasites of South African wildlife. II. Helminths of kudu, tragelaphus strepsiceros, from South West Africa/Namibia

A total of 23 kudu, Tragelaphus strepsiceros, were shot at 2-month intervals from June 1983 to April 1984 in the Etosha Game Reserve in the north of South West Africa/Namibia. The parasite survey conducted on these animals yielded 2 cestode and 12 nematode species. Haemonchus vegliai and Cooperia neitzi were the most prevalent nematodes and occurred in 13 animals each, followed by Cooperia acutispiculum and an Onchocerca sp. (9 animals each). The remaining nematodes were present in 4 (17%) or fewer of the antelope. C. neitzi was the most numerous nematode, a total of 3,564 being recovered from all the antelope, followed by C. acutispiculum (2,552) and H. vegliai (1,050). Individual total worm burdens varied from 4-1,326 with 2 kudu harbouring no worms. The mean burden of 399 worms was considered negligible. A single kudu was shot in the Namib-Naukluft Park in the south of the country. This animal harboured no parasites.     

Electrocardiography of Grevy's zebras (Equus grevyi)

Electrocardiograms (ECGs) are a good baseline test for assessing cardiac rhythm. ECGs have not been reported in any zebra species and in very few Perissodactyla species. Standard limb, six-lead ECGs were recorded in 23 anesthetized Grevy's zebras (Equus grevyi). Heart rate, RR interval, P-wave duration, RR maximum/minimum, PR interval, QRS duration, QT interval, ST segment deviation, P-wave amplitude, QRS amplitude, and T-wave amplitude were measured and calculated from lead II ECGs from these Grevy's zebras. Several variables were tested, including gender, age (0-24, 24-48, 48-180, and >180 mo), weight (<350 kg or >350 kg), pregnancy status, and anesthetic differences (standard dose or supplemented dose), to see if they affected ECG values in these animals. There were no significant differences in any of the ECG parameters between genders. RR and QT intervals were longer in older zebras; heart rates were faster in younger zebras. The RR and PR intervals, as well as the QRS duration, were greater in heavier zebras; heart rates were faster in lighter zebras. The RR interval was significantly longer in pregnant zebras. There were no significant differences in any of the ECG parameters for zebras anesthetized with a standardized dose of the drug combination etorphine-detomidine-acepromazine compared to those receiving additional supplements of these drugs and/or ketamine. All other parameters were not significantly different among groups, except where noted previously. The results of this research indicate that differences in ECG parameters in zebras may occur between animals of different ages, weights, and pregnancy status and that these factors should be considered when interpreting the respective ECGs of these zebras.     

Halicephalobus gingivalis (Nematoda) infection in a Grevy's zebra (Equus grevyi).

A 6-yr-old female Grevy's zebra (Equus grevyi) with a disseminated rhabditiform nematode infection is described. Antemortem clinical signs were limited to blindness and abnormal behavior believed to be caused by a recurrent nematode-induced uveitis. Histologic examination of the kidneys, heart, eyes, uterus, and lymph nodes revealed granulomas containing multiple sections of rhabditiform nematodes. Most of the recovered nematodes were larval stages with only a few adult females noted. The adults measured 243-297 microm x 11-16 microm (x = 269 x 14 microm). The distinctive rhabditiform esophagi had corpus:isthmus:bulb proportions of 19:11:5. On the basis of adult morphology, the nematode was identified as Halicephalobus gingivalis. This is the first report of this parasite in a zebra and indicates that this parasitic granulomatous disease should be considered in zebras with neurologic disease.