Resistance and resilience of traditionally managed West African Dwarf goats from the savanna zone of northern Nigeria to naturally acquired trypanosome and gastrointestinal nematode infections.

A survey was conducted of gastrointestinal nematode infections and trypanosomosis in Nigerian West African Dwarf (WAD) goats from the savanna region of the country. Animals were screened at two markets, Gboko and Akpagher, from the beginning of April until the end of September, coinciding with the end of the dry season and the first 5 months of the wet season. Of 1054 goats that were examined, 80.5% carried gastrointestinal (GI) nematodes belonging to the genera Haemonchus (61.0%), Oesophagostomum (21.0%) and Trichostrongylus (17.9%). Faecal egg counts (FEC) increased very slowly but significantly from April to maximum levels in September, and varied marginally between the two market sources. The majority of goats (68.8 and 70.1% at the two markets) had low FEC not exceeding 50 eggs/g (epg). FEC did not differ significantly between the sexes or between age classes. Packed cell volume (PCV) also declined significantly with month of the study, but was affected by host sex (a significant month x sex interaction) being generally higher in male animals throughout the period. There was a highly significant negative correlation between log10(FEC+1) and PCV, when all other factors had been taken into account. Body condition scores (BCS) also declined with month of the study, but there was a marked difference between the two sexes, with male animals generally showing a greater stability of BCS across the months compared with females. Trypanosome infections were found in only 4% of the goats and only during the rainy season. Most infections (92.86%) were caused by Trypanosoma brucei alone although T. vivax and T. congolense were occasionally detected. Overall, the majority of goats sampled each month maintained generally good body condition (BCS 3.0-5.0), normal or slightly reduced PCV, even when concurrently infected with trypanosomes and GI nematodes. However, four concurrently infected goats showed signs of overt anaemia during periods of peak infection, during the late rainy season, with marked reductions in PCV (< 15%). Two of the infected goats were also in poor body condition with BCS of < 2.0. There was no evidence of additive or synergistic pathogenic effects of the two parasites. These results are discussed in the context of the unexpectedly strong resistance and resilience of the savanna WAD ecotype to its native strains of GI nematode and trypanosome parasites.

Quantitative trait loci for resistance to Heligmosomoides bakeri and associated immunological and pathological traits in mice: comparison of loci on chromosomes 5, 8 and 11 in F2 and F6/7 inter-cross lines of mice.

A comparison of F2 and F6/7 inter-cross lines of mice, derived from CBA and SWR parental strains, has provided strong evidence for several previously undetected quantitative trait loci (QTL) for resistance to Heligmosomoides bakeri. Five QTL affecting average faecal egg counts and/or worm burdens in week 6 were detected on mouse chromosomes 5 (Hbnr9 and Hbnr10), 8 (Hbnr11) and 11 (Hbnr13 and Hbnr14). Three QTL for faecal egg counts in weeks 4 and 6 were found on both chromosomes 5 (Hbnr9) and 11 (Hbnr13 and Hbnr14). Two QTL for the mucosal mast cell protease 1 (MCPT1) response were located on chromosomes 8 (Hbnr11) and 11 (Hbnr13), two for the IgG1 antibody response to adult worms on chromosomes 5 (Hbnr10) and 8 (Hbnr11), two for PCV in week 6 on chromosomes 5 (Hbnr9) and 11 (Hbnr13), and two for the granulomatous response on chromosome 8 (Hbnr12) and 11 (Hbnr15). Our data emphasize that the control of resistance to H. bakeri is multigenic, and regulated by genes within QTL regions that have a complex range of hierarchical relationships.

Evaluation of the anthelminthic potential of Duranta erecta L. (Verbenaceae) fruits used in Nigerian ethnomedicine as a vermifuge.

ETHNOPHARMACOLOGICAL RELEVANCE: Duranta erecta L. fruits have been reported to have in vitro anthelminthic properties. People living in the tropical South-Eastern part of Nigeria use the plant in folk medicine for the treatment of malaria, abscesses and as a vermifuge. Although there are a few reports about its in vitro anthelminthic activity against different worm categories, scientific reports regarding its in vivo anthelminthic activity are limited. AIM OF THE STUDY: This study was designed with the aim of determining the potential of the plant as an anthelminthic and to verify the claims made by its local users. MATERIALS AND METHODS: Acute toxicity of the plant extract was determined using Lorke's method. Anthelminthic activity was investigated using adult male albino mice experimentally infected with Heligmosomoides bakeri infective L3. Graded ascending doses of the plant extract and Albendazole respectively were orally administered to the mice in the infected groups. Corprological and haematological parameters were recorded within the study period. Twenty-eight (28) days post-infection, all infected mice were humanely sacrificed and the Post-Mortem Adult Worm Burden (WB) was estimated and recorded. RESULTS: The results showed that the extract had an LD50 greater than 5000 mg/kg BW and therefore was not acutely toxic for oral use. It also showed that the plant extract was unable to eliminate the faecal egg output or adult worms in the gastrointestinal tract of infected animals even at the high doses used in the study. This was in contrast to Albendazole which significantly (p < .05) reduced faecal egg counts and worm burdens by 71% and 92% respectively in treated mice. Following infection, there was anaemia in all infected groups seen from results of erythrocytic parameters. Treatment with the plant extract, regardless of the dose, was unable to effectively reverse the effect of parasite infection on erythrocytic parameters. However, treatment with Albendazole positively reversed the anaemia, restoring the mice to pre-infection values by the end of the experiment. The results showed significant (p < .05) increase in WBC counts across all groups following infection with the parasite. Treatment with the plant extract and Albendazole respectively, significantly (p < .05) reduced the WBC counts to near pre-infection values in most treatment groups. CONCLUSION: As a result of the poor anthelminthic effects recorded in the study, it is therefore recommended that Duranta erecta L. fruits be explored for its other useful effects rather than as an anthelminthic.

Global warming is changing the dynamics of Arctic host-parasite systems.

Global climate change is altering the ecology of infectious agents and driving the emergence of disease in people, domestic animals, and wildlife. We present a novel, empirically based, predictive model for the impact of climate warming on development rates and availability of an important parasitic nematode of muskoxen in the Canadian Arctic, a region that is particularly vulnerable to climate change. Using this model, we show that warming in the Arctic may have already radically altered the transmission dynamics of this parasite, escalating infection pressure for muskoxen, and that this trend is expected to continue. This work establishes a foundation for understanding responses to climate change of other host-parasite systems, in the Arctic and globally.

Parenterally administered gastrointestinal nematode infective larvae viable after more than 15 years in liquid nitrogen.

After cryopreservation for 13.3-15.8 years, the viability of the infective larvae (L3) of Trichostrongylus axei, T. colubriformis, Oesophagostomum columbianum, Haemonchus contortus, Ostertagia circumcincta, T. falculatus, Nematodirus spathiger, Chabertia ovina and Dictyocaulus filaria was assessed in sheep, by being deposited at their predilection sites. D. filaria was, however, an exception, in that the L3 were injected into the jugular vein. The mean development of all the species was 22.8%, but if three species (O. columbianum, C. ovina and D. filaria), that developed poorly are disregarded, then the mean development was 33.4%, similar to previous tests after shorter periods of cryopreservation. The L3 of some of the species appeared sluggish when examined 10-15 min after being thawed, and in the case of H. contortus practically all the larvae of the original batch tested in the previous trials of the series appeared dead when thawed for use in the present trial, and were replaced by another batch of L3 of the same species. When re-examined after about 8 h, however, a high percentage of the L3 of the original batch appeared to have become revitalised, and their viability was tested in a trial reported elsewhere. The intestinal cells of the majority of the L3 of N. spathiger, O. circumcincta and C. ovina were vesiculated when they were thawed. Nevertheless, the degree of development of the former two species was of the highest in the trial, and it can be concluded that this phenomenon does not necessarily impede the viability of larvae.

Assessment of domestic goats as a patent host of Elaphostrongylus cervi.

A study was undertaken to determine whether domestic goats can serve as patent hosts of Elaphostrongylus cervi under natural or experimental conditions. Three-hundred and two fecal samples from 124 domestic goats raised outdoors in New Zealand, where E. cervi is enzootic, were tested for nematode larvae by the Baermann method. All samples were negative for E. cervi dorsal-spined larvae. Twenty juvenile male Nubian and Saanen goats obtained locally were assigned randomly to 5 dosage groups and were orally administered 5, 15, 35, 65, or 125 third-stage larvae of E. cervi, respectively. Two yearling female red deer (Cervus elaphus elaphus) each received 35 or 65 third-stage larvae as positive controls, and 2 uninoculated juvenile male goats served as negative controls. Fecal Baermann testing of pooled samples from the inoculated goats was conducted weekly for the first 80 days postinoculation (DPI) and daily thereafter until 250 DPI. No dorsal-spined larvae were recovered. One goat that had received 15 third-stage larvae displayed a mild transient posterior ataxia suggestive of cerebrospinal elaphostrongylosis. Gross postmortem examination did not reveal any direct evidence of nematodes in any of the goats, and only a few minor lesions were present. Histologically, these lesions were consistent with a parasite etiology. Histological evaluation of grossly normal lumbar and sacral spinal cord from 2 goats that had each received 125 third-stage larvae revealed eosinophilic meningoencephalitis and leukomyelitis, respectively, suggestive of the presence of parasites in the central nervous system. The 2 positive control red deer became patent with dorsal-spined larvae consistent with E. cervi at 131 DPI. These findings suggest that goats, at least those breeds utilized in this study, are not suitable patent hosts for E. cervi.

Estimating transmission potential in gastrointestinal nematodes (order: Strongylida).

Microparasite virulence (the potential to cause harm in the host) is thought to be regulated by a direct trade-off with pathogen transmission potential, but it is unclear whether similar trade-offs occur in macroparasites (helminths). In this analysis, the transmission potentials of 5 nematode species (order Strongylida), known to differ in their virulence, were estimated using an index based on egg production and larval survivability. Virulence estimates were based on the minimum number of worms that cause host death. In nematode species where mature adults cause pathology (trichonematidic development), there is a direct relationship between virulence and transmission, suggesting that high virulence is related to parasite fitness in these worms. However, in nematodes where the juvenile stages produce pathology during migration and development (strongylidic development), virulence is not correlated with transmission. These data suggest that trade-offs between transmission and virulence in nematode parasites are not analogous for all species and may depend on the developmental strategy and mechanism of pathogenicity of the parasites.

Experimental Elaphostrongylus alces infection in goats.

Five goats aged 4 months were each inoculated with approximately 300 third-stage larvae of Elaphostrongylus alces, and killed for post-mortem examination after 14-150 days. No clinical signs of disease were observed during the experiment. Pathological examination revealed that the larvae penetrated the walls of the abomasum and small intestine and migrated towards the caudal vertebral canal. However, the great majority of larvae were apparently destroyed along the migratory route, and development to adult parasites in the vertebral canal was not seen. During migration, the larvae caused focal inflammation and necrosis in the gastrointestinal wall, liver, mesentery and lungs. The study suggests that the only effect of E. alces infection on goats is the formation of focal visceral lesions during abdominal larval migration; it also confirms the infectivity of E. alces for domestic ruminants.

Mortality of Creole kids during infection with gastrointestinal strongyles: a survival analysis.

Mortality due to strongyles infection in small ruminants is a critical component of flock productivity in a tropical climate. In goat production, few experiments have been conducted to estimate the variability of this trait. A survival analysis study was carried out in the Creole experimental flock of INRA-Gardel (Moule, Guadeloupe) to identify management and genetic factors influencing mortality of kids reared at pasture and infected with gastrointestinal strongyles, predominantly Haemonchus contortus and Trichostrongylus colubriformis. Survival curves from 3 and 11 mo of age were analyzed for 837 kids sired by 48 bucks and 250 does. The causes of death were recorded. Mortality due to gastrointestinal strongyles was the variable considered. The flock management included drenchings with levamisole every 8 wk. Fecal egg counts and packed cell volume were regularly measured after 7 wk of natural infection. All but 6.7% of the records were uncensored, with an average failure time of 165 d. The probability of death following gastrointestinal infection was more than three times greater in males than in females. Kids raised by their mother before weaning had a lower (P < 0.05) relative risk of dying than those reared in nursery (0.40 vs. 1). Parity of the dam and litter size effects were not significant. The risk of death was reduced by approximately 80% during the 3 wk that followed a drenching (P < 0.01). Risk decreased by about 25% for each additional kilogram of body weight at weaning. Live weight, fecal egg counts, and packed cell volume all had significant effects on risk of death when introduced as time-dependent covariates in the model (P < 0.0001 for live weight and packed cell volume, and P < 0.01 for fecal egg counts). The estimated genetic variability was small and inaccurate. These results demonstrated that risk of death from gastrointestinal infection could be reduced with appropriate flock management. High infection levels increased the risk of death, but they were not the direct cause. The important mediation of reduced body weight and anemia in likelihood of death is highlighted. More data are needed to better assess the possibility for genetic improvement of viability in Creole kids during gastrointestinal strongyle infection.

Successful immunization against a parasitic nematode by vaccination with recombinant proteins.

Infection of humans and livestock with parasitic nematodes can have devastating effects on health and production, affecting food security in both developed and developing regions. Despite decades of research, the development of recombinant sub-unit vaccines against these pathogens has been largely unsuccessful. We have developed a strategy to identify protective antigens from Teladorsagia circumcincta, the major pathogen causing parasitic gastroenteritis in small ruminants in temperate regions, by studying IgA responses directed at proteins specific to post-infective larvae. Antigens were also selected on the basis of their potential immunomodulatory role at the host/parasite interface. Recombinant versions of eight molecules identified by immunoproteomics, homology with vaccine candidates in other nematodes and/or with potential immunoregulatory activities, were therefore administered to sheep in a single vaccine formulation. The vaccine was administered three times with Quil A adjuvant and the animals subsequently subjected to a repeated challenge infection designed to mimic field conditions. Levels of protection in the vaccinates were compared to those obtained in sheep administered with Quil A alone. The trial was performed on two occasions. In both trials, vaccinates had significantly lower mean fecal worm egg counts (FWECs) over the sampling period, with a mean reduction in egg output of 70% (Trial 1) and 58% (Trial 2). During the period of peak worm egg shedding, vaccinates shed 92% and 73% fewer eggs than did controls in Trials 1 and 2, respectively. At post mortem, vaccinates had 75% (Trial 1) and 56% (Trial 2) lower adult nematode burdens than the controls. These levels of protection are the highest observed in any system using a nematode recombinant sub-unit vaccine in the definitive ruminant host and indicate that control of parasitic helminths via vaccination with recombinant subunit vaccine cocktails is indeed an alternative option in the face of multi-drug resistance.

Gastrointestinal parasites in goats from Monte Castelo, Santa Catarina, Brazil / Parasitas gastrintestinais em caprinos de Monte Castelo, Santa Catarina, Brasil

This study was carried out with the aim of estimating the degree of gastrointestinal helminth infection in goats on the Northern Plateau of Santa Catarina. Twelve young females and 11 adult females were used. Every 28 days, feces samples were taken to quantify the nematode eggs per gram of feces (EPG). Larval culturing was performed on a pool of positive samples from the same group. The fecal egg counts (FECs) ranged from zero to 10,400 EPG in the young group and zero to 7,600 EPG in the adult group. The mean FECs were between 583.3 and 4441.7 in the young group and between 418.2 and 2181.8 in the adult group. Eggs of the order Strongylida and genera Moniezia and Toxocara, and oocysts of Coccidia, were observed. The young animals were more affected and Haemonchus was the most prevalent genus in the samples.

Este trabalho foi realizado com o objetivo de estimar o grau de infecção dos helmintos gastrintestinais em um rebanho caprino criado no Planalto Norte Catarinense. Foram utilizadas 12 fêmeas jovens e 11 adultas, das quais, a cada 28 dias, foram coletadas amostras de fezes diretamente do reto, totalizando 12 coletas, para quantificação de ovos por grama de fezes (OPG) e cultivo de larvas através de "pool" das amostras positivas do mesmo grupo. A contagem de OPG variou de zero a 10.400 nos animais jovens e de zero a 7.600 nos adultos. As médias do OPG entre as coletas foram de 583,3 a 4.441,7 no grupo jovem e de 418,2 a 2.181,8 nos adultos, sendo observados ovos da ordem Strongylida, dos gêneros Moniezia e Toxocara, bem como oocistos de coccídeos. Os animais mais jovens foram os mais acometidos, sendo o gênero Haemonchus o mais prevalente.