Responses of the humid zone ecotype of the Nigerian West African Dwarf sheep to mixed infections with Haemonchus contortus and Trichostrongylus colubriformis.

The responses of the Nigerian West African Dwarf sheep to experimental infections with two of its most important gastrointestinal (GI) nematodes, namely, Haemonchus contortus and Trichostrongylus colubriformis were studied by means of two measures of parasitological response, namely, faecal egg count (FEC) and worm burden (Wb), and three measures of host pathology, namely, packed cell volume (PCV), body weight (Bwt) and body condition score (BCS). Following exposure to weekly escalating infections (60% H. contortus and 40% T. colubriformis) starting with single doses of 500 infective larvae (L(3)) at week 1, 1,000 L(3) at week 2, 2,000 L(3) at week 3 and 4,000 L(3) at week 4, two distinctive worm burden response phenotypes were readily recognisable, namely, low Wb (LWb) and high Wb (HWb) phenotypes. The percentage of inoculums (adults and immature stages) recovered at necropsy were 3.75% and 33.08% respectively for H. contortus and T. colubriformis. The results showed that the FECs of the lambs belonging to the LWb phenotype were significantly lower than the FECs of their HWb counterpart. Among the measures of host pathology tested, the LWb phenotype sheep had similar Bwt, PCV and BCS to the uninfected control sheep, whereas the HWb phenotype sheep had significantly lower values than their LWb counterparts and the control sheep towards the end of the experiment. There was a highly significant positive correlation between worm burden transformed as log(10) (Wb + 10) and the average of D56 and D59 FECs. A highly significant negative correlation also was obtained between log(10) (Wb + 10) and the PCV, Bwt and BCS. The low percentage of H. contortus inoculums recovered at necropsy suggested that the sheep may be resistant to their most important GI nematode, H. contortus but less so to T. colubriformis.

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.

The effect of dietary protein on the productivity of West African Dwarf (WAD) goats infected with Haemonchus contortus.

The effects of increased dietary protein on the performance of West African Dwarf (WAD) goats infected with Haemonchus contortus were investigated. 28 pubertal 9-12-month-old female goats were divided into two equal groups A and B and fed on high and low protein diets, respectively, from day 1 of pregnancy (day of mating) to 6 weeks post-partum. Each animal was trickle infected with a total of 2400 infective larvae of H. contortus over 4 weeks starting from day 1 of pregnancy and the prepatent period recorded. Live weights and body condition scores were measured weekly and the changes determined by subtracting the initial value from each of the subsequent values. Birth and weaning weights of kids as well as stillbirths and foetal loses were also determined. High protein diet improved the ability of goats to resist worm establishment and patency, which was manifested as significant increase in the prepatent period in group A than in the low protein diet group B (p<0.001). Also high protein diet resulted in significantly higher increase in body weight during pregnancy (p<0.01). During lactation both groups rapidly lost weight although body weight increase relative to preinfection value remained significantly higher in group A than B (p=0.05). Between weeks 3 and 13 post infection, the body condition scores increased but were significantly higher in group A than in group B (p<0.001). From weeks 16 to 27, the body condition scores remained significantly higher in group B than group A although both experienced severe losses during lactation. Group A delivered significantly heavier kids than group B (p<0.001) and had no foetal losses as occurred in the latter. However, the level of supplementation had no influence on weaning weights as there was no significant difference in the weaning weights of kids of both group (p>0.05). It is concluded that lactation demand for dietary protein is higher than that for gestation since both body weights and body condition scores deteriorated in both group during lactation, and that improved dietary protein enhances resistance to parasite establishment (increased prepatent period) and resilience in terms of kidding performance, birth weight and survival of neonates.

Naturally occurring variability in some phenotypic markers and correlates of haemonchotolerance in West African Dwarf goats in a subhumid zone of Nigeria.

West African Dwarf (WAD) goats of the Nigerian subhumid zone generally show strong resistance and resilience to Haemonchus contortus in laboratory experiments, although a relatively small proportion are susceptible to infection. Little is known about these extremes of response phenotype in nature. Therefore, a survey was carried out of gastrointestinal nematode infections in WAD goats, with emphasis on abomasal worms, at three goat markets in Southern Nigeria during the rainy season. Faecal samples (n=1070) were collected weekly from goats between April and September, and 352 abomasa and small intestines from local abattoirs were examined. Total strongyle (prevalence=65.0%) and H. contortus (prevalence=64.3%) faecal egg counts (FEC) varied between the three markets, being highest throughout at Opi. FEC increased from April to peak in August. Based on raw FEC, 76.1% of goats had FEC of <100, and 4.7%>500. Adjustment of these figures for monthly and between-market differences, gave figures of 78.8 and 3.4%, respectively. H. contortus worm burdens (WB) showed a similar pattern with 67.9% of goats harbouring <200 worms and 8.2% >1000, and after adjustment 69.6 and 6.0%, respectively. Fecundity, based on eggs in the uterus, did not vary between markets or monthly, but fell with increasing WB. Trichostrongylus colubriformis was less frequent (prevalence=42.4%) but goats from Opi also carried higher WB, and worms were similarly highly aggregated in hosts. When the between-market and monthly differences for both species were controlled, a highly significant positive correlation between the species emerged. Therefore, although a small subset of goats, highly susceptible to H. contortus, exists in this breed, the majority show resistance under field conditions and the resistant phenotype is also resistant to T. colubriformis. Both species are highly aggregated in the susceptible subset of the population. While, we cannot yet exclude alternative explanations, our data are compatible with a strong genetic basis for this phenomenon.

Expression of acquired immunity to a local isolate of Haemonchus contortus by the Nigerian West African Dwarf goat.

The capacity of young Nigerian West African Dwarf (WAD) goats to express good acquired immunity to their native geographic strain of Haemonchus contortus and the correlates of this responsiveness were studied in a laboratory experiment involving forty 7-8 month old kids. A primary immunising infection with 2000 L3 (equivalent to 260-450 L3/kg body weight) with or without challenge on D42 with 2000 L3 resulted in a mild chronic infection with a pre-patent period of 18-20 days and little or no reduction in worm burden between D14 and D56. In contrast, another group (D) of kids, whose immunising infection had been truncated with fenbendazole on D35 and later received similar challenge infection, developed good protection against challenge. Thus, worm burdens were largest in group E (challenge control), larger in group C (primary+challenge) and least in group D. Of the measures of infection used, namely faecal worm egg counts (FECs), circulating eosinophil (EOS) responses, packed cell volume (PCV) and body weight, FEC and EOS responses exhibited marked individual variability, but only FEC (geometric mean of transformed counts) and PCV showed strong correlation with worm burden. There was also a significant negative correlation between FEC and PCV. The size of inoculum used was well tolerated by the kids, as it induced only mild changes in PCV in some goats and no effect at all on body weights. This suggests that the WAD goat may possess a good measure of resistance to the pathogenic effects of its native strain of H. contortus. The wide individual variability in FEC and its strong relationships to worm burden and PCV are pointers to its likely genetic basis. There are, therefore, good prospects for further studies to identify H. contortus resistant genotypes among the WAD goat population.

The response of Nigerian West African Dwarf goats to experimental infections with Haemonchus contortus.

One option for controlling haemonchosis in warm pastoral regions is improvement of resistance by selective breeding. Variation in acquired immunity to H. contortus and immunological correlates of infection were studied in West African Dwarf (WAD) goats. Following exposure to 5000 L3, 63 per cent of the inoculum established but 77 per cent of established worms were expelled by week 5. All infected animals were anaemic (day 14). When exposed to 2000L3, 36 per cent of the inoculum was still present (day 35) with no loss by day 49. Persisting primary infection worms survived a superimposed challenge (day 35), but their growth was slowed and resistance to challenge was significant. Most goats showed eosinophilia and parasite-specific IgG responses to primary infection, but only eosinophilia increased after challenge. No consistent associations were found between parasite burden and any immunological measures of infection, but parasite egg counts showed considerable variation. Overall, our results suggest that resistant genotypes exist among the WAD goat population.

Correlates of resistance to gastrointestinal nematode infection in Nigerian West African dwarf sheep.

OBJECTIVE: To investigate correlates of resistance to GI nematode infection in Nigerian West African dwarf (WAD) sheep. METHODS: Thirty three sheep were randomly assigned to two groups, A (n=27) which were used for experimental infections, and B (n=6) which served as uninfected control. Each infected animal received weekly escalating infections with infective larvae (60%Haemonchus contortus (H. contortus) and 40%Trichostrongylus colubriformis (T. colubriformis) for 4 weeks. The responses of all the infected and control sheep were assessed by faecal egg count (FEC), worm burden (Wb), packed cell volume (PCV), body weight (Bwt), and body condition score (BCS). On the basis of their individual faecal egg output, Lambs in group A with epg ≤1,000 on any sampling day were classified as low faecal egg count (LFEC) phenotype (n=16), those with epg between 1,000 and 10,000 as intermediate (n=5) and lambs with epg > 10,000 as high feacal egg count (HFEC) phenotype (n=6). RESULTS: The difference between the FEC classes was highly significant (P=0.001). The BCS and weight gained at the end of the experiment by the control and LFEC sheep was significantly higher (P≤0.05) than those of the intermediate and HFEC phenotypes. There was a significant and negative correlation between the parasitological measures and the trio of BCS, PCV and Bwt of sheep. CONCLUSION: The result of the study indicated that the FEC, weight gain, PCV, and BCS are correlates and potential selection criteria of GI nematode resistant WAD sheep.

Changes in the body condition scores of Nigerian West African Dwarf sheep experimentally infected with mixed infections of Haemonchus contortus and Trichostrongylus colubriformis.

Weekly changes in body condition scores and body weights were determined in West African Dwarf sheep following trickle exposure to weekly escalating mixed infections with Haemonchus contortus and Trichostrongylus colubriformis starting with single doses of 500 infective larvae (L(3)) at wk1, 1000 L(3) at wk2, 2000 L(3) at wk3 and 4000 L(3) at wk4. Thirty-three animals were randomly assigned to two groups namely, Group 1 (n=27) and Group 2 (n=6). Group 1 animals were used for experimental infections and Group 2 animals served as uninfected controls. Body condition scores (BCS), body weights (BW), faecal egg counts (FEC) per gram of faeces and worm burden (Wb) were determined using standard procedures. Lambs in group 1 with epg ≤ 1000 were classified as strong responders (n=16), those with epg between 1000 and 10,000 as intermediate (n=5) and lambs with epg>10,000 on any sampling day were classified as weak responders (n=6). Based on this classification, the mean epg of lambs classified as strong responders was significantly lower (P<0.001) than the epg of lambs classified as weak responders. The body condition scores and body weights of the strong responder lambs were comparable with those of the uninfected control and they were significantly higher than those of the weak and intermediate responders from wk5 till the end of the experiment. There was an inverse and significant relationship between the average BCS of days 56 and 59 and the average FEC of days 56 and 59 (r(s)=-572; P=0.017; n=27) as well as with Wb (r(s)=-531; P=0.028; n=27). We concluded that changes in the body scores are good indicators of the intensity of gastrointestinal nematode infection in the Nigerian WAD sheep.

A cross-sectional survey on parasites of chickens in selected villages in the subhumid zones of South-eastern Nigeria.

A study was carried out to identify and estimate the prevalence of ecto- and endoparasites of village chicken between April and July 2008 in three local councils of Enugu state, Nigeria. A total of 1038 chickens comprising of 468 chicks, 207 growers and 363 adults were examined during the house to house survey for ectoparasites, gastrointestinal helminths and coccidia infections. Our finding showed that 41% were infected with ectoparasites with lice, fleas, and mites having prevalence rates of 62.2%, 35.7% and 2.1%, respectively. Helminths and coccidia had prevalence of 35.5% each. Among the helminths Ascaridia, galli was the most dominant species (17.2%). Generally, there was a significantly higher helminth infestation relative to the ectoparasites (P < .05), high prevalence of mixed infections and absence of tick infestation. Parasitism could be big constraint to production in the study area and we recommend a sustainable control strategy.

The impact of dietary protein on the pathophysiology of porcine trypanosome infection.

The influence of protein nutrition on porcine trypanosomosis was investigated in this study. Thirty six landrace/large white cross weanling pigs were used. Upon purchase, these were divided into two groups of 18 pigs each and these were housed separately to enable them adapt to our animal house management regimen. Post-adaptation, the pigs were divided into 6 groups A(1) and A(2), B(1), and B(2), and C(1) and C(2) (n=6). A(1) and A(2) were fed diet A(1), B(1) and B(2) diet B while C(1) and C(2) were fed diet C with 28%, 20% and 16% crude protein, respectively. Two-week post-adaptation groups A(1), B(1), and C(1) were infected with 3×10(6)Trypanosoma brucei brucei organisms intraperitoneally. Body weight, temperature and Packed Cell Volume of all group members were determined a week prior to infection, on the day of infection and weekly thereafter till end of the study. Serum biochemistry was also concurrently determined. Three days post-infection, blood was collected from all the members of A(1), B(1) and C(1) and thoroughly screened microscopically for the presence of trypanosome organisms. This was repeated on subsequent days till all the infected animals developed patency by showing parasitaemia under wet mount. The result of this study showed that infection did not have any significant effect on the rate of weight gain except in group C (p≤0.05). Moreover, infections caused significant hyperthermia in all the infection groups (p≤0.05) with diet A showing the least response and C the most severe. Furthermore, diet did not have any effect on parasite establishment or parasitaemia as the prepatent period was similar in all the infection groups. There was also significant reduction in PCV whose severity also correlated with reduction in the protein dietary quality. Similar observation was also made on the total serum protein where significant hyperproteinaemia correlated with increasing dietary protein and the uninfected controls having higher serum protein relative to the infected. There was in addition parasite induced hypoalbuminaemia whose severity was also graduated in favour of increasing protein level. The study demonstrated the protective influence of dietary protein on some of the pathophysiological features of porcine trypanosomosis.

Resistance and resilience of West African Dwarf goats of the Nigerian savanna zone exposed to experimental escalating primary and challenge infections with Haemonchus contortus.

We assessed the resilience and resistance to infection with Haemonchus contortus of savanna West African Dwarf (WAD) goats from northern Nigeria. Adult male goats (n=32) were given an escalating immunizing infection, comprising 5 weekly infections with increasing numbers of larvae. On day (D) 56 they were segregated into low (LFEC) and high (HFEC) faecal egg count phenotypes, and within each phenotype 7 goats were treated with anthelmintic and seven received no treatment. Four goats were culled for worm counts. Fourteen additional goats acted as naïve controls until D56. All, except seven naïve, were challenged with 6000 L3 of H. contortus on D63 and culled on D81, together with the seven naïve goats. The escalating infections had no effect on body weight of the goats. Neither deworming, nor challenge infection and previous experience of infection influenced body weight post-challenge (pc). There was no effect of the escalating infection on packed cell volume (PCV) of blood cells, however, the HFEC phenotypes tended to have lower values than their LFEC counterparts and controls towards the end of immunization. Virtually all goats maintained normal PCV values (28-32%) throughout, without clinical evidence of anaemia. After challenge infection the HFEC phenotypes had significantly lower PCV than the LFEC goats and naïve controls but without other symptoms of anaemia. Anthelmintic treatment had no influence on PCV pc. The anthelmintic-treated LFEC group harboured fewer worms on D18 pc than the untreated LFEC group with the superimposed challenge. In contrast anthelmintic treatment made only a small difference to the worm burdens of the HFEC group pc. In week 7 there was a strong correlation between FEC and PCV among all the goats that experienced the immunizing infection. With anthelmintic treatment taken into account, higher FEC and lower PCV in week 7 predicted higher worm burdens at the end of the experiment, but both relationships were dependent on and differed between the anthelmintic treatment groups. Overall, we found no parasitological evidence of attenuation or loss of resistance and resilience of the Nigerian savanna WAD goat ecotype to H. contortus, suggesting that significant introgression of genes from parasite-susceptible Sahelian breeds into this WAD goat population has so far not occurred.