The role of parasite epidemiology in the management of grazing cattle

Epidemiology of ruminant helminths is the foundation on which strategic parasite control programmes are designed. Without this information one is not able to use anthelmintics to provide the optimal benefits for controlling both the adult worm and the pasture larval populations. The absence of strategic programmes generally results in using anthelmintics at the convenience of the producer, which may have little if any impact on parasite populations. The design of a strategic parasite control programme requires a knowledge of the dynamics of egg shedding from the host and the resulting pasture larval populations. It is important to know if larvae are available when animals are turned out onto pasture, when larval populations reach their maximal numbers and when they are induced to become hypobiotic. The goal is to keep pasture larval populations as low as possible. The use of pasture rotation adds another dimension to control programmes. The longer a pasture is allowed to remain fallow, the lower the pasture larval burden will be when it is grazed next. However, when we use intensive rotational grazing, animals may return to the pasture about 28 days later, when the larvae resulting from the eggs shed in the previous grazing are infective. This practice forces cattle to eat all of the forage available, including the grass closest to the faecal pat, where most of the infective larvae are available. If we treated cattle before turning them onto a clean rotationally grazed pasture, we should be able to control parasitism. Using a long-acting anthelmintic should enhance helminth control in rotationally grazed pastures and actually help to clean the pastures. Another grazing management practice is to alternately graze different species. This programme with the strategic use of anthelmintics should reduce parasitism in both host species.

The role of epidemiological knowledge and grazing management for helminth control in small ruminants

There is no single requirement more crucial to the rational and sustainable control of helminth parasites in grazing animals than a comprehensive knowledge of the epidemiology of the parasite as it interacts with the host in a specific climatic, management and production environment. In its absence, anthelmintic treatment is either given suppressively, which provokes resistance, or therapeutically, which risks clinical disease and production losses. Sustainable parasite-control programmes require knowledge of seasonal larval availability, origin of larvae contributing to any peaks and climatic requirements for worm egg hatching, larval development and survival. Control measures based on this knowledge include strategic anthelmintic treatments and various forms of grazing management. While these measures can reduce the frequency of anthelmintic treatment required, their effect on selection for drench resistance is more problematical, unless they can be combined with other forms of control to reduce our current dependence on anthelmintics.

Habitat related differences in helminth parasites of red foxes in the Ebro valley

The prevalences of helminth parasites found on red foxes collected in two different habitats of the Ebro Valley, in north-eastern Spain were compared. Twenty helminth species, including one trematode, six cestodes, 12 nematodes and one acanthocephalan were found. Metorchis albidus, Uncinaria stenocephala and Dirofilaria immitis were more prevalent in the irrigated lands close to the main rivers of the study area, whereas Trichuris vulpis and Pterygodermatites affinis showed higher prevalences in the semiarid stepparian habitat. Habitat characteristics need to be considered when surveying helminths over large geographical areas. The study shows that in the Ebro Valley the fox constitutes a reservoir host for several helminth species that are parasites of the domestic dog or the wolf, or may have importance as zoonoses.

Gastrointestinal helminths of four gekkonid lizards, Gehyra mutilata, Gehyra oceanica, Hemidactylus frenatus and Lepidodactylus lugubris from the Mariana Islands, Micronesia

The gastrointestinal tracts of gekkonid lizards from Guam (Gehyra mutilata [n = 4], Gehyra oceanica [n = 11], Hemidactylus frenatus [n = 43], and Lepidodactylus lugubris [n = 38]) and Rota (Gehyra oceanica [n = 2], Hemidactylus frenatus [n = 13], and Lepidodactylus lugubris [N = 20] were examined for helminths. Found were 2 species of cestodes, Cylindrotaenia allisonae, Oochoristica javaensis, 1 species of trematode, Allopharynx macallisteri, and 5 species of nematodes, Pharyngodon lepidodactylus, Spauligodon gehyrae, Spauligodon hemidactylus, Skrjabinelazia machidai, Oswaldocruzia sp. New host records included Gehyra mutilata for Spauligodon hemidactylus, Gehyra oceanica for Oochoristica javaensis, Hemidactylus frenatus for Skrjabinelazia machidai, and Lepidodactylus lugubris for Cylindrotaenia allisonae and Oswaldocruzia sp. These helminths are known only from Pacific Islands and the Australian biogeographic realm.

Helminth and protozoan gastrointestinal tract parasites in captive and wild-trapped African non-human primates

The objective of this study was to investigate the gastro-intestinal (GIT) parasites commonly occurring in captive and wild-trapped (WT) non-human primates (baboons, vervets and Sykes) in Kenya and compare their prevalence. Three hundred and fifteen faecal samples were subjected to a battery of diagnostic tests, namely, direct smear, modified formal ether sedimentation, Kato thick smear, Harada-Mori techniques for parasite detection and culture to facilitate nematode larvae identification. Of these, 203 (64.4%) harboured helminths and 54 (17.1%) had protozoa. The helminth parasites comprised Strongyloides fulleborni 141 (44.8%), Trichuris trichuira 200 (63.5,%), Oesophagostomum sp. 48 (15.2%), Trichostrongylus sp. 73 (23.2%), Enterobius vermicularis 44 (14.0%), Schistosoma mansoni 4/92 (4.3%) and Streptopharagus sp. 68 (21.6%). Protozoan parasites consisted of Entamoeba coli 204 (64.8%), Balantidium coli 127 (40.3%) and Entamoeba histolytica 78 (24.8%). Both WT and colony-borne (CB) primates had similar species of parasites, but higher prevalences of protozoan infection were observed in CB baboons while helminth infections were relatively more common in WT primates. Some of the parasites observed in this study are reported to be zoonotic in various parasitological literatures. Chemoprophylaxis and other managerial practices were believed to be responsible for the lower worm prevalence in CB primates. Similar intervention against protozoa and other agents will not only improve primate health, but also increase safety to animal handlers and colony workers.

Metazoan parasites of the red rockfish Sebastes capensis off northern Chile

The parasites of the red rockfish Sebastes capensis off northern Chile are described quantitatively for the first time and compared with those of congeneric species of the Northern Hemisphere as well as of other Chilean marine fishes. Sixteen species were recorded, including 8 ectoparasites (2 copepods, 2 isopods, 1 turbellarian, and 3 monogeneans) and 8 endoparasites (2 acanthocephalans, 3 digeneans, and 3 nematodes). The ectoparasites Lepeophtheirus chilensis and Caligus cheilodactylus, and the endoparasites Pseudopecoelus sp. and Corynosoma sp. were predominant. Eighty percent of the fishes harbored 3-6 parasite species. Four parasite genera new to the genus Sebastes were found in S. capensis, which also shares several parasite genera with its congeneric species from other geographic areas. However, in contrast to its congeners, S. capensis exhibits a lower helminth species richness, although when all the metazoan fauna is considered the species number and diversity are similar. When compared with other demersal fishes of the Chilean coast, S. capensis shows a high number of species and high parasite abundance. Diphtherostomum sp. and Gnathia sp. are new generic records for the parasite fauna of Chilean coast fishes and the finding of Paramicrocotyle sp., Neobenedenia melleni, and Interniloculus chilensis in this study represents a new geographical record for these parasites.

A survey of helminth infection in rats (Rattus spp) from Chiang Mai Moat

An investigation of helminths in the Norway (brown) rat, Rattus norvegicus, and roof rat, Rattus rattus, from Chiang Mai Moat during May to August 1995, was done. Thirty-three out of thirty-eight trapped rats were infected (86.84%); 16 R. norvegicus (100%) and 17/22 R. rattus (77.27%). The rat was infected with 10 helminth species: 4 trematodes, Centrocestus sp (2.63%), Echinostoma ilocanum (10.52%), Echinostoma malayanum (10.52%) and Quinqueseralis quinqueseralis (39.47%); 2 cestodes, Raillietina sp (36.64%) and Taenia sp (cysticercus) (7.89%); and 4 nematodes, Angiostrongylus cantonensis (42.10%). Nippostrongylus sp (34.21%), Rictularia sp (52.63%) and egg of Capillaria hepatica (7.89%). The helminths were found in the small intestine (84.21%), large intestine (42.10%), lung (36.64%), stomach (28.94%), heart (23.94%), and liver (15.78%). The female Norway rats were infected with 10 species of helminths and the males with 6 species. In the roof rat, 7 species of helminths were found in females and 6 species in males.

Interactive mortality factors in common loons from Maritime Canada

Between August 1992 and November 1995, 31 moribund or dead common loons (Gavia immer) found in the three Maritime provinces of Canada (New Brunswick, Nova Scotia, Prince Edward Island) were necropsied. Eight of these birds were in good body condition and died acutely from drowning or trauma. The remaining 23 birds were in poor body condition and had either chronic lead poisoning, respiratory mycosis, or oil contamination of their plumage. Loons in poor body condition had significantly higher numbers of intestinal trematodes and significantly higher levels of total renal mercury than loons in good body condition. Therefore, poor body condition in many loons was associated with two or more concurrent potential disease processes, although we could not establish a cause-effect relationship among these processes in individual birds. These results suggest that mortality in chronically ill wild animals can result from synergism among several potentially debilitating agents present in their environment.

Etiology and prophylaxis of helminthiasis in sheep in Burkina Faso

Helminths of "Mossi" sheep from traditional livestock were investigated at three different seasons (humid, cold dry, and hot dry seasons) in the village of Donsin from the central land of Burkina Faso. Three prophylaxis plans using Fenbendazole were tested. Primary parasites identified were: Oesophagostomum sp., Trichostrongylus sp., and Haemonchus contortus. These parasites were noticed mainly during the rainy season with mean egg per gram (epg) numbers of 500 +/- 141.42 in August-September, at the end of the rainy season. At this same period, hematocrit (22%) and body weights (17 kg of live weight) (LW) were low. These values progressively increased to reach their highest levels (32% and 27 kg of LW respectively) in February. The prophylactic plan consisting of two treatments with oral drench of 5 mg/kg LW of Fenbendazole turned out to be the most efficacious and the most economical.

Helminth levels of working donkeys kept under different management systems in the Moretele 1 district of the North-West Province, South Africa

In Southern Africa, where 150,000 working donkeys provide an important alternative to mechanisation in resource-poor communities, very little is known about their helminth status, or about the impact of helminths on their work output. The aim of this study was to investigate the helminth status of working donkeys under different management systems. Donkey owners in three different areas (one rural and two semi-rural) of the Moretele 1 district of North-West Province, South Africa, were visited and structured interviews were used to assess the management systems under which the donkeys were kept. Faecal samples were collected from 93 donkeys in the study once a month for 14 months. Faecal samples were analysed for nematode and trematode eggs and cultured to produce third-stage larvae for the identification of the nematode species. Final comparisons between management system subgroups, as well as between areas, age groups and sexes were made. Four management systems were identified. (1) The first system identified consisted of donkeys which were kept in a small yard at all times. They were fed hay but no supplementary food. (2) The second system consisted of donkeys which were allowed to roam freely around the village most of the time and rounded up and held in an enclosure when needed for work. (3) The third system was identical to the second management system except that the donkeys were given supplementary food during winter. (4) The fourth system was only found in the one area where each owner owned 10 ha of land and here the donkeys were allowed to roam freely on the owner's land and brought into enclosures prior to working. Helminth species composition and faecal egg count numbers differed between these four systems. The main difference noted was that donkeys from management system one showed significantly higher numbers of strongyle eggs and higher percentages of some of the strongyle larvae. Management system two had a higher Strongyloides mean egg count and prevalence than the other areas. Parascaris and Gastrodiscus egg counts differed between all four systems. Since the results showed differences in the number and species of helminths in donkeys kept under the four management systems, suggestions are made as to which management system would facilitate reduction of helminth parasites in the animals. Although supplementary feeding in Moretele 1 is fairly rare, it would seem that donkeys which do have access to better food resources have lower egg counts than donkeys on limited grazing.

Comparison of three estimators of species richness in parasite component communities

Comparisons of species richness between parasite component communities are often confounded by uneven sampling effort and the possibility that rare species have been missed from some component communities. The use of nonparametric estimators of species richness could potentially alleviate this problem by allowing the number of missing species to be extrapolated from the observed data. The performance of 3 estimators and their sensitivity to true species richness and the frequency of rare species, i.e., species with low prevalence, were tested using computer-simulated parasite communities. When the number of hosts examined in a sample is large, the observed species richness is an accurate estimate of true richness; no extrapolation is necessary even when rare species make up a large part of the community. At small sample sizes, observed species richness is a poor underestimate of true richness. The jackknife estimator and Chao's estimator both improve the estimate of species richness, but they are imprecise and can seriously overshoot the true richness value when the community includes many rare species. The bootstrap estimator. on the other hand, gives a better estimate than observed richness. Bootstrap estimates are also less variable and less likely to overestimate true richness, independently of how frequent rare species are in the community. This estimator provides a better, but conservative, estimate of true richness than observed richness and should be used to correct for inadequate host sampling. Data from natural communities suggest that the use of richness estimators is often justified, and that many parasite species may regularly escape detection.

Gastrointestinal helminths of loggerhead turtles (Caretta caretta) from the western Mediterranean: constraints on community structure

Richness and composition of gastrointestinal helminth communities of 54 loggerhead turtles, Caretta caretta, from the western Mediterranean were interpreted from patterns of helminth exchange at 2 host taxonomic scales: exchange between marine turtles and other marine hosts and exchange within turtles. We predicted exchange of the former to be unimportant ecologically and evolutionarily because of the host phylogenetic distance. The absence of records of successful exchange at this host taxonomic scale confirmed that host physiological barriers seem to prevent contemporary parasite transfer between marine turtles and other sympatric hosts. Marine turtles also seem to exhibit an evolutionary association with their parasites largely independent from that of other marine hosts. Therefore, the composition of gastrointestinal helminth communities of marine turtles is predictably restricted to digeneans, nematodes, and aspidogastreans specific to these reptiles. At the scale of host species, helminth exchange among marine turtle species was expected to be significant. This was suggested by reports indicating a high proportion of parasites common to all sea turtle species. Mediterranean C. caretta harbored only 4 digenean species typical of marine turtles, and immature individuals of 1 digenean species accidentally acquired. Further, no relevant parasite exchange with other marine turtles was expected to occur because C. caretta is the only sea turtle species abundant in the western Mediterranean. Therefore, a predictable composition coupled with low species richness in infracommunities might be accounted for partly by constraints on parasite acquisition at both host scales. Host factors limiting parasite recruitment (mainly ectothermy and a wandering behavior) may also contribute to depauperate and isolationist infracommunities.

Australian helminths in Australian rodents: an issue of biodiversity

The Australian public as well as Australian funding bodies are generally unsympathetic to native murids, rats and mice, in spite of the fact that 36% have either become extinct or critically endangered since European settlement. The endemic Australian parasites of these rats and mice have been even less sympathetically regarded. Prior to 1958 very little work was carried out on the helminths of Australian rodents and little more is known today. Records are known from only 28% of the extant host species, comprising some 109 species of helminth identified at least to generic level. The rodents invaded Australia from the north, perhaps through New Guinea in at least two separate waves, 5-8 then about 1 million years ago. The parasites they brought with them have adapted and speciated and there has been some host switching between rodent groups and between rodents and the Australian marsupials. This is illustrated particularly in the Trichostrongyloidea. The origins of the rodents from Southeast Asia down the Indonesian island chain are reflected in the presence of the nematode genus Tikusnema in both Australia and Indonesia, and Cyclodontostomum purvisi across Southeast Asia and into New Guinea. Hydromys chrysogaster, the Australian water-rat, illustrates how the biogeographical influences of the host's distribution and lifestyle can affect its parasite fauna. Most of the research to date is merely indicative of where more data are needed. The links between Australian and New Guinean helminth fauna, as well as the links between rodent and marsupial hosts and their fauna, cannot be determined without further research.

Macroparasites in cetaceans stranded on the northwestern Spanish Atlantic coast

An extensive parasitological survey was carried out during autopsy of 80 cetaceans representing 8 species within 4 families (Delphinus delphis, Stenella coeruleoalba, Tursiops truncatus, Grampus griseus, Globicephala melas, Kogia breviceps, Phocoena phocoena and Megaptera novaeangliae) collected on the northwestern Spanish Atlantic coast from February 1991 to October 1996. Two species of tetraphyllidean cestodes (Phyllobothrium delphini and Monorygma grimaldii), 2 ascaridoid nematodes (Anisakis simplex and A. physeteris), a single spirurid nematode (Crassicauda magna), 4 rhabditidiform nematodes (Halocercus delphini, H. invaginatus, Halocercus spp. and Stenurus globicephalae), a single polymorphynae acanthocephalan (Bolbosoma sp.), and 2 amphipods (Isocyamus delphini and Cyamus boopis) were found. This paper presents 6 new geographic records of macroparasites from cetaceans in temperate Atlanto-Iberian waters. A total of 11 component parasite species were found, mainly parasitizing the blubber, mesentery and stomach of cetaceans. Cetaceans harboured a suite of 4 generalist and 8 specialist species.

Comparative performance of species richness estimation methods

In most real-world contexts the sampling effort needed to attain an accurate estimate of total species richness is excessive. Therefore, methods to estimate total species richness from incomplete collections need to be developed and tested. Using real and computer-simulated parasite data sets, the performances of 9 species richness estimation methods were compared. For all data sets, each estimation method was used to calculate the projected species richness at increasing levels of sampling effort. The performance of each method was evaluated by calculating the bias and precision of its estimates against the known total species richness. Performance was evaluated with increasing sampling effort and across different model communities. For the real data sets, the Chao2 and first-order jackknife estimators performed best. For the simulated data sets, the first-order jackknife estimator performed best at low sampling effort but, with increasing sampling effort, the bootstrap estimator outperformed all other estimators. Estimator performance increased with increasing species richness, aggregation level of individuals among samples and overall population size. Overall, the Chao2 and the first-order jackknife estimation methods performed best and should be used to control for the confounding effects of sampling effort in studies of parasite species richness. Potential uses of and practical problems with species richness estimation methods are discussed.

Northern bobwhites as disease indicators for the endangered Attwater's prairie chicken

Because of limited access to the endangered Attwater's prairie chicken (Tympanuchus cupido attwateri), we used a related species, the northern bobwhite (Colinus virginianus), as a surrogate for disease evaluation. Free-living northern bobwhites (n = 62) on the Attwater Prairie Chicken National Wildlife Refuge (near Eagle Lake, Texas, USA) were examined during spring and fall 1993 for helminthic endoparasites and specific antibodies against the infectious agents responsible for nine infectious diseases. Trichostrongylus cramae, Raillietina sp., and Strongyloides avium were collected from 97, 44, and 32% of northern bobwhites examined, respectively. Dispharynx nasuta and Syngamus trachea also were found. No gross lesions due to parasites were observed. Specific antibody to Pasteurella multocida was found in 3 of 53 plasma samples. It is possible that potentially pathogenic species such as P. multocida, T. cramae, and D. nasuta could threaten sympatric Attwater's prairie chickens.

Latitudinal differences in species and community richness and in community structure of metazoan endo- and ectoparasites of marine teleost fish

Relative species diversity of gastrointestinal helminths of 55 teleost fish species did not differ significantly at different latitudes, whereas relative species diversity of metazoan ectoparasites on the heads and gills of 108 teleost fish species showed a significant increase with decreasing latitude and from deep to surface waters. Abundance of endoparasites also was the same at all latitudes, whereas abundance of ectoparasites increased with decreasing latitude and from deep to shallow waters. A comparative analysis using phylogenetically independent contrasts supported these conclusions. Possible reasons for the differences between endo- and ectoparasites are discussed. A detailed analysis of the community structure of gastrointestinal helminths of five Antarctic and three tropical teleosts and of metazoan ectoparasites on the heads and gills of five Antarctic and seven tropical fish species showed the following: abundance and prevalence of infection of endoparasites are similar in Antarctic and tropical fish, but are much greater for tropical than for Antarctic ectoparasites. Relative species diversity of endoparasites is similar for Antarctic and tropical endoparasites, but much greater for tropical than Antarctic ectoparasites. In both Antarctic and tropical fish, different fish of the same species may have different dominant species of endo- and ectoparasites, although there is a greater range of dominant species of tropical ectoparasites, a consequence of the greater species pool available. The most dominant parasite (irrespective of species) represented 80-99% of all endoparasites of Antarctic, and about 50-80% of all endoparasites of tropical fish. The most dominant parasites (irrespective of species) represented about 90-100% of all ectoparasites of Antarctic, and about 20-70% of all ectoparasites of tropical fish, the difference a consequence of the greater species pool of tropical ectoparasites available. The data suggest that both endo- and ectoparasites live in assemblages not structured by interspecific competition.

Gastrointestinal helminth parasites in stray cats from the mid-Ebro Valley, Spain

Gastrointestinal helminths were collected from 58 necropsied stray cats (Felis catus) in the mid-Ebro Valley, North-East Spain, from December 1989 to March 1992. The prevalence was 89.7%, with those of individual parasites being Toxocara cati 55.2%C, Ancylostoma tubaeforme 29.3% Joyeuxiella pasqualei 55.2%, Diplopylidium acanthotetra 20.7%, Dipylidium caninum 20.7%, Mesocestoides spp. 13.8%, Taenia taeniformis 8.6% and Diplopylidium nölleri 8.6%. In relation to sex, the differences were not significant. However, the season of the year significantly affected the prevalence of A. tubaeforme and D. acanthotetra.

The contributions of host age and size to the aggregated distribution of parasites in yellow perch, Perca flavescens, from Garner Lake, Alberta, Canada

The independent effects of host age and size on parasite abundance are examined in yellow perch from Garner Lake in east-central Alberta. Older, larger perch tend to have more species of parasites combined with larger parasite infrapopulations. Sexual size dimorphism in perch generates 2 different size classes within each age class >2+ yr, thus allowing the opportunity to separate the effects of age and size on the recruitment of parasites by perch. The abundances of Diplostomum adamsi and Bothriocephalus sp. both increase with host age, whereas the increased abundances of Crepidostomum isostomum and Raphidascaris acus in larger fish are, in part, suggestive of size-specific feeding behaviors of the host. A combination of parasites with size- and age-dependent infrapopulations results in a size-dependent increase in infracommunity size. A comparison of variance-to-mean ratios within age classes to overall variance-to-mean ratios shows that the effects of host age and size on parasite recruitment do contribute to parasite aggregation.

Helminth parasites of conventionally maintained laboratory mice--II. Inbred strains with an adaptation of the anal swab technique

Worm burdens recovered from inbred mice strains, namely C57Bl/6, C57Bl/10, CBA, BALB/c, DBA/2 and C3H/He, conventionally maintained in two institutional animal houses in the State of Rio de Janeiro, RJ, Brazil, were analyzed and compared, regarding their prevalences and mean intensities. Three parasite species were observed: the nematodes Aspiculuris tetraptera, Syphacia obvelata and the cestode Vampirolepis nana. A modification of the anal swab technique is also proposed for the first time as an auxiliary tool for the detection of oxyurid eggs in mice.

Origin of an insular population of the wood mouse based on parasitological evidence

Parasitological data were used to test the hypothesis that the wood mouse (Apodemus sylvaticus) population of Fair Isle, Shetland, originated from the British Isles rather than Scandinavia, as is usually argued. This study was based on the assumption that the mice were likely to share most of their parasite fauna with conspecifics from their ancestral home. The ecto- and endo-parasites of wood mice on Fair Isle between 18 June to 10 July 1987 and 17 to 26 August 1991 were identified and compared with those reported from conspecifics in the two putative source areas. All eight species of metazoan parasites that infected A. sylvaticus on Fair Isle were common to mice of the British Isles, whereas just one parasite on Fair Isle, a mite, had been recorded from Scandinavia. This lends support to the hypothesis that the mice originated from Britain rather than Scandinavia.

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.

Helminth surveillance as a prerequisite for anthelmintic treatment in intensive sow herds

Helminth prevalences in pigs in intensive production systems are often very low due to housing and management factors, and the present study was carried out to examine whether routine anthelmintic treatment in such herds can be replaced by coprological surveillance of the helminth status combined with anthelmintic treatment when necessary. After an initial examination, 25 out of 28 large herds of Danish sows (> or = 50 sows, production of fatteners) were found to have such light helminth infections that routine deworming could be replaced experimentally by coprological examination every 6 months of 10 weaners (10-12 weeks old), 10 fatteners (5-6 months old), 10 dry sows and 10 lactating sows. This coprological surveillance continued in 21 herds of the selected 25 herds for a 3-year period, while it was stopped immediately in one herd due to increasing Ascaris suum prevalences, and ceased after one year in three herds due to other reasons. A. suum was found in all but one of the 25 herds. The most heavily infected age group was the sows, in which the A. suum prevalence was consistently low in approximately half of the herds, while it increased slowly or rapidly in the other half. When this happened, treatment of the breeding stock was recommended which resulted in low prevalences for varying periods of time. Few farmers neglected the recommendations for some time or for all 3 years, which resulted in consistently high prevalences in the sows (e.g. 40-60%). The fatteners were in general more lightly infected with A. suum than the sows, and in approximately 3/4 of the herds the prevalence remained at a low level, while it fluctuated in the remaining herds. No weaners were ever found to excrete eggs, most likely due to unfavourable conditions for egg development in the farrowing pens. Throughout the study Oesophagostomum sp. eggs were found sporadically in the sows of two herds, and in a third herd, Oesophagostomum sp. was introduced after 2 years, probably due to close contact with a neighbour herd. Oesophagostomum sp. was not found in the remaining herds. Eggs of Trichuris sp. were found sporadically. In conclusion, it is recommended that veterinarian advisers evaluate the production systems before suggesting an anthelmintic routine. If helminth infections may be controlled by intensive management and housing alone, coprological surveillance combined with anthelmintic treatment when necessary may replace routine use of anthelmintics. If the surveillance reveals that the infection levels continue to be low unnecessary medication is avoided, and if the infection levels increase, the coprological data obtained can be used to optimize the anthelmintic strategy.

Parasites of South African wildlife. XV. Helminths of scrub hares, Lepus saxatilis in the Kruger National Park

A total of 145 scrub hares from three localities in the Kruger National Park were examined for helminths: 124 at Skukuza, 15 at Shingwedzi, and three each at Pretoriuskop and Pafuri. Trichostrongylus deflexus was the most prevalent and most abundant nematode, and was collected from hares from all four localities. Trichostrongylus falculatus was present in three localities. Trichostrongylus thomasi and Dermatoxys vlakhaasi occurred only at Skukuza in 50 and 23%, respectively, of the hares examined. The cestode Mosgovoyia pectinata and the nematode genus Impalaia were each recovered from three localities and Cooperia hungi from two. There was no apparent seasonal pattern of abundance of the worms, and the intensities of infection of male and female hares were similar. With the exception of D. vlakhaasi, all the helminths recovered in this study represent new records for scrub hares in South Africa.