Recombinant elongation factor 1 alpha of Haemonchus contortus affects the functions of goat PBMCs.

Excretory/secretory proteins of Haemonchus contortus (HcESPs) intermingle comprehensively with host immune cells and modulate host immune responses. In this study, H contortus ES antigen named as elongation factor 1 alpha (HcEF-1α) was cloned and expressed. The influences of recombinant HcEF-1α on multiple functions of goat peripheral blood mononuclear cells (PBMCs) were observed in vitro. Immunoblot analysis revealed that rHcEF-1α was recognized by the serum of goat infected with H contortus. Immunofluorescence analysis indicated that rHcEF-1α was bound on surface of PBMCs. Moreover, the productions of IL-4, TGF-ß1, IFN-γ and IL-17 of cells were significantly modulated by the incubation with rHcEF-1α. The production of interleukin IL-10 was decreased. Cell migration, cell proliferation and cell apoptosis were significantly increased; however, nitric oxide production (NO) was significantly decreased. The MHC II molecule expression of cells incubated with rHcEF-1α was increased significantly, whereas MHC-I was not changed as compared to the control groups (PBS control and pET32a). These findings indicated that rHcEF-1α protein might play essential roles in functional regulations of HcESPs on goat PBMC and mediate the immune responses of the host during host-parasite relationship.

Dynamic transcriptomic changes of goat abomasal mucosa in response to Haemonchus contortus infection.

Gastrointestinal nematode (GIN) infections are one of the major constraints for grazing sheep and goat production worldwide. Genetic selection for resistant animals is a promising control strategy. Whole-transcriptome analysis via RNA-sequencing (RNA-seq) provides knowledge of the mechanisms responsible for complex traits such as resistance to GIN infections. In this study, we used RNA-seq to monitor the dynamics of the response of the abomasal mucosa of Creole goat kids infected with Haemonchus contortus by comparing resistant and susceptible genotypes. A total of 8 cannulated kids, 4 susceptible and 4 resistant to GIN, were infected twice with 10 000 L3 H. contortus. During the second infection, abomasal mucosal biopsies were collected at 0, 8, 15 and 35 days post-infection (dpi) from all kids for RNA-seq analysis. The resistant animals showed early activation of biological processes related to the immune response. The top 20 canonical pathways of differentially expressed genes for different comparison showed activation of the immune response through many relevant pathways including the Th1 response. Interestingly, our results showed a simultaneous time series activation of Th2 related genes in resistant compared to susceptible kids.

Behavioural and productive response to experimental infection with stage 3 larvae of Haemonchus contortus in feedlot bull-calves.

Haemonchus contortus is a nematode parasite that establishes in the abomasum of ruminants, it has a cosmopolitan distribution and is a worldwide health problem for livestock. As a first line of defence against parasites, behaviour can help to prevent or fight infection, and may even serve as a method of early presumptive diagnosis. Parasites can affect performance of cattle and cause significant economic losses. The aim of this study was to determine the behavioural and productive changes induced by an experimental infection with H. contortus L3 in bovines. We used 32 dewormed bull calves, randomly divided into two groups, 8 no inoculated controls and 24 that were inoculated with 4000 L3 of H. contortus. Inoculation did not influence haematocrit or haemoglobin values at 0, 28 and 42 days post infection (P> 0.20); however, an increase in the frequency of urination (P = 0.0001) and defecation (P = 0.0001), number of steps (P < 0.001) and self-grooming (P < 0.01) events were observed, even in inoculated animals in which not parasite eggs were found in faeces. During the first 28 days post-inoculation with H. contortus, feedlot performance was not affected (P = 0.16), but during the last 14 days (29-42) inoculated animals gained 15% less weight compared to controls (P = 0.04). Over 42 days, inoculated calves showed a 28% poorer feed efficiency during the 42 days post-inoculation than controls (P < 0.01). Across the experiment, calves inoculated with H. contortus obtained less net energy both for maintenance as for gain from diet (P < 0.01). It is concluded that both, performance and behaviour were modified in feedlot bull-calves parasitized by H. contortus, supporting the practice of deworming when eggs of this parasite are detected in the faeces even in low amounts.

The nutritional status affects the complete blood count of goats experimentally infected with Haemonchus contortus.

BACKGROUND: Gastrointestinal nematode (GIN) remains the most important pathogenic constraint of small ruminant production worldwide. The improvement of the host immune response against GIN though breeding for improved animal resistance, vaccination and nutritional supplementation appear as very promising methods. The objective of this study was to investigate the effect of four nutritional status differing in protein and energy levels (Hay: 5.1 MJ/Kg of dry matter (DM) and 7.6% of crude protein (CP), Ban: 8.3 MJ/Kg of DM and 7.5% of CP, Soy: 7.6 MJ/Kg of DM and 17.3% of CP, BS: 12.7 MJ/Kg of DM and 7.4% of CP) on the haematological disturbances due to Haemonchus contortus infection in Creole kid goats. RESULTS: No significant effect of the nutritional status was observed for faecal egg count (FEC) but the experimental infection induced haematological disturbances whose intensity and lengthening were dependent on the nutritional status. A transient marked regenerative macrocytic hypochromic anaemia as revealed by a decrease of packed cell volume (PCV), red blood cells (RBC) and hemoglobin and an increase of reticulocytes was observed in all infected groups except Hay. In this latter, the anaemia settled until the end of the experiment. Furthermore, H. contortus induced a thrombocytopenia significantly more pronounced in the group under the lowest nutritional status in term of protein (Hay and Ban). A principal component analysis revealed that the variables that discriminated the nutritional status were the average daily gain (ADG) and the PCV, considered as measures of the level of resilience to H. contortus infection. Moreover, the variables that discriminated infected and non-infected animals were mostly related to the biology of RBC (i.e. size and hemoglobin content) and they were correlated with FEC. CONCLUSIONS: The severity and the lengthening of the regenerative anaemia and the thrombocytopenia induced by H. contortus have been affected by the nutritional status. The protein enriched diets induced resilience to the infection rather than resistance. This suggests that resilience is associated with an improved regenerative capacity of the bone marrow. However, this needs to be further investigated to understand the relationships between resistance, resilience and dietary supplementation.

Nitrogen retention in hair sheep lambs with a gradient of Haemonchus contortus infection.

The impact of Haemonchus contortus infections on nitrogen retention (NR) of hair sheep lambs is unknown. This study estimated the feed intake, digestibility, NR, haematocrit (HT), and their relationship with the gradient of H. contortus infection in hair sheep lambs. Twenty-four hair sheep lambs, 3-4 months old, reared parasite-free were used (live weight (LW) 16.7 ± 1.7 kg). Six lambs were kept parasite-free, nine lambs received a dose of 300 H. contortus infective larvae (L3)/kg LW, and the remaining nine lambs received 500 H. contortus L3/kg LW. Infection doses ranged from 3870 to 9,500 L3. Lambs were individually fed for an average daily gain (ADG) of 100 g. On days 1 (P < 0.01) and 7 (P < 0.001) post-infection (PI), the L3 doses were positively associated with HT, possibly due to platelet recruitment. On week 1 PI, the infection (L3) reduced the crude protein (CP) intake (g/kg metabolic LW) (P < 0.05). A reduction of 1% HT corresponded to 1200 eggs per gram of faeces (EPG) for day 21 PI (P < 0.05), 2300 EPG for day 28 PI (P < 0.001), 2400 EPG for day 35 (P < 0.001), and 1300 EPG for day 41 PI (P < 0.001). However, the HT levels were never lower than 21 %. A lower CP digestibility was associated with EPG only on week 5 PI (P < 0.05). There was no significant association between EPG, Total egg in faeces, or worm burden (WB) with intake, dry matter digestibility (DMD), ADG or NR. The NR of lambs was positive along the different weeks of study irrespective of infection level. The WB was negatively associated only with HT on day 41 PI (P < 0.001), where a 1 % HT reduction was estimated for every 257 worms hosted. In conclusion, no relationship was found between H. contortus infection and DMD, ADG or NR in hair sheep lambs. The cost of H. contortus infection resulted only from the HT reduction and depended on the gradient and stage of the infection.

Effect of the nutritional status of Creole goats on the density-dependent prolificacy of Haemonchus contortus.

The objective of this study was to measure the effect of the nutritional status of Creole goat kids on the host responses and the nematode population established after an experimental H. contortus infection. Fifty six kids were fed with 4 diets corresponding to 2 nutritional statuses: the low nutritional status (HAY, hay ad libitum and HB, Hay ad libitum + banana) and the high nutritional status (HS, hay ad libitum + soya meal and HSB, hay ad libitum + banana + soya meal). For each diet, 8 kids were experimentally infected with 10,000 H. contortus infective larvae (L3) and 6 kids were kept as non-infected controls. From the day of infection until 6 weeks post-infection, samples were collected to measure individual intake, total tract digestibility, parasitological and hematological parameters. The dry matter intake (DMI), the average daily gain (ADG), the crude protein (CP) and the digestible CP intake were higher in goats fed the HS and HSB diets, but no statistically significant interaction between the nutritional status and the infection was observed. The packed cell volume (PCV), the red blood cell counts (RBC) and the mean corpuscular volume (MCV) were higher with the HS and the HSB diets. In kids with the high nutritional status the nematode burden and pathophysiological impact of the infection were significantly lower but not the FEC. In conclusion, this reduced establishment rate was associated with an increased production of eggs by the female parasites and suggested a phenomenon of density-dependent prolificacy of H. contortus probably inherent to the fitness of the parasite population.

Self-selection of plant bioactive compounds by sheep in response to challenge infection with Haemonchus contortus.

Plant bioactives can potentially benefit herbivores through their effects on health and nutrition. The objective of this study was to determine the importance of polyphenols and terpenes on the ability of lambs to self-select these compounds when challenged by a parasitic infection and the subsequent impact on their health and productivity. Thirty-five lambs were housed in individual pens and assigned to five treatment groups (7 animals/group), where they received: 1) A basal diet of beet pulp:soybean meal (90:10) (CONTROL); 2) The same diet, but containing 0.3% of bioactive natural plant compounds extracted from grape, olive and pomegranate (BNP); 3) A simultaneous offer of the diets offered to the Control and BNP groups (Choice-Parasitized; CHP-1); 4) The Control diet, and when lambs developed a parasitic infection, the choice described for CHP-1 (CHP-2); and 5) The same choice as CHP-1, but animals did not experience a parasitic burden (Choice-Non-Parasitized; CHNP). Lambs, except CHNP, were dosed with 10,000 L3 stage larvae of Haemonchus contortus. Infected lambs under choice treatments (CHP-1 and CHP-2) modified their feeding behavior in relation to the CHNP group as they increased their preference for the feed containing polyphenols and terpenes, interpreted as a behavior aimed at increasing the likelihood of encountering medicinal compounds and nutrients in the environment that restore health. This change in behavior corresponded with an improvement in feed conversion efficiency. However, an increased preference for the diet with added plant bioactives did not have an effect on parasitic burdens, hematological parameters, blood oxidation, or serum concentration of IgE.

The effect of dietary protein supplementation on the pathophysiology of Haemonchus contortus infection in West African Dwarf goats.

The effect of dietary protein on the pathophysiology of Haemonchus contortus infection in reproducing first pregnancy West African Dwarf (WAD) goats was studied. Eighteen 10-12-month-old pubertal female WAD goats divided into two equal groups were used and confined separately. One group was maintained on high-protein diet (HPD) while the other was maintained on low-protein diet (LPD) from day 1 of pregnancy up to week 6 post-partum. Each animal was infected with 600 infective larvae of H. contortus weekly for 4 weeks and blood collected by jugular venipuncture for the determination of packed cell volume and serum proteins. The results of the study showed that improved protein nutrition significantly enhanced the level of serum albumin (p<0.05). It also significantly lowered the level of serum globulin (p<0.05) that otherwise would be high in haemonchosis. However, improvement in the dietary protein level appeared not to have any effect on the packed cell volume and total serum protein level.

Performance, endoparasitary control and blood values of ewes locally adapted in semiarid region.

This study evaluated the variation in the prevalence of endoparasitoses and their impact on body condition and blood values of sheep of the Morada Nova breed. A total of 138 ewes were examined for their morphology (body weight, BW; body condition score, BCS), parasitology (faecal egg count, FEC; Famacha© score; coproculture), hematology (red blood cell count,RBC); hemoglobin concentration, HE; packet cell volume, PCV; mean corpuscular volume, MCV,; mean corpuscular hemoglobin, MCH; mean corpuscular hemoglobin concentration, MCHC; leukocytes, WBC) and serum biochemistry (glucose, cholesterol, triglycerides, urea, creatinine, total protein, albumin, globulin, AST and ALT). Overall the animals presented higher BW and BCS in the months of September and December, however, with high FEC, in addition to a large number of animals with Famacha score 4 and 5. The results showed that the main hematophagous worm affecting the sheep, the genus Haemonchus ssp, appeared in a greater proportion (30-71.66%) than the other worms in all months of the study, except in March. About 30% of the hematological values found in the study are outside the reference ranges for suable sheep e 45.50% for serum biochemistry. These findings demonstrate the most healthy period of the year was from March to June for endoparasites control, however, in the months of September and December the animals showed better performance measures.

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.

[Physiopathological mechanisms of abomasal Trichostrongylidae infections in small ruminants]. / Meccanismi fisiopatogenetici dei principali tricostrongilidi abomasali dei piccoli ruminanti.

Abomasal Trichostrongylidae infections are still today an important cause of scarce performances in small ruminants, mainly when bred in extensive systems. Although morpho-biology, symptomatology, prophylaxis and therapy of these infections are well known, other, such as physiopathology, are less investigated. The aim of the present note is to review the more important physiopathogenetic mechanisms of abomasal Trichostrongylidae infections, with special emphasis to Haemonchus spp. and Teladorsagia spp. The parasitic anorexia due to the action of gastrin, the defects of digestion due to hypocloridia, the scarce intestinal absorption and anaemia caused by H. contortus are discussed. Furthermore, the effects of hypersensitivity sometimes caused by these abomasal nematodes are examined. A better knowledge of physiopathological mechanisms can represent an important factor to understand the relationships between host and parasite, useful to set up new diagnostic techniques or new therapeutic and prophylactic protocols for sanitary education and control plans of these important and widespread parasitic infections.

Impact of the post-weaning nutritional history on the response to an experimental Haemonchus contortus infection in Creole goats and Black Belly sheep.

In small ruminants, the response against gastrointestinal nematode (GIN) infections is influenced not only by the host genotype and the physiological stage but also by environmental factors, particularly the nutritional status at the time of infection. In this study we evaluated the long-term effect and the interaction between the host species and the nutritional history on the response to GIN infection in two animal models differing in their phenotypic growth and their level of GIN resistance: Black Belly sheep and Creole goats. Lambs and kids were subjected to three distinct nutritional conditions at weaning: low dietary conditions (100% of the theoretical energy requirement for maintenance, corresponding to 548v. 484KJ/Kg BW(0.75) for lambs and kids respectively and 6% of crude protein, CP), medium dietary conditions (150% of the theoretical energy requirement for maintenance and 13% CP) and high dietary conditions (200% of the theoretical energy requirement for maintenance and 20% CP). This 3-months period was followed by a 1-month period on the medium dietary conditions for all the animals before an experimental Haemonchus contortus infection. We monitored the impact of the nutritional history (nutritional condition after weaning), on the intensity of the GIN infection by measuring individual faecal egg counts (FEC), growth rate (ADG), blood eosinophil counts and other pathophysiological parameters. The FEC, growth rate and blood eosinophil counts were significantly affected by the nutritional history in lambs but not in kids. The lowest FEC was found for lambs placed in high dietary conditions, however during the same period body weight loss was observed in this group. In low dietary conditions, kids were more resistant than lambs and the ADG was higher in lambs. However, the anaemia and the level of serum pepsinogen, marker of the abomasal mucosa integrity, were higher in kids. Our data suggest that the impact of the post-weaning nutritional history on the response to an experimental H. contortus infection is significantly affected by the host species.

Exploring the limitations of pathophysiological indicators used for targeted selective treatment in sheep experimentally infected with Haemonchus contortus.

Identifying which sheep to treat as part of a Targeted Selective Treatment approach to gastro-intestinal nematode control relies entirely on the efficacy of the indicators. Indicators such as FAMACHA© (anaemia), DISCO (diarrhea) and reductions in weight gains were designed specifically to reflect those sheep experiencing symptomatic consequences of infection. Using the gastro-intestinal nematode Haemonchus contortus as a model species, this study explored the utility and sensitivity of these indicators under controlled experimental conditions on 63 adult sheep. The potential effect of sheep with different H. contortus resistance phenotypes on indicator efficacy was compared in three different phenotypes, i.e. high (Blackbelly females), medium (Blackbelly rams) and low resistance (Romane rams). The potential effect of the H. contortus isolate on indicator efficacy was also explored by using four different isolates, with varying anthelmintic resistance capacities, to infect the sheep. We limited the study to the first month of infection to evaluate the interest of these indicators as an early predictive means for controlling infection. The pathophysiological indicators FAMACHA© and DISCO do not reflect infection intensity based on Faecal Egg Counts, nor do reductions in weight gains. FAMACHA© was however a good indicator of anaemia with strong correlations to haematocrit. There was little agreement among the three indicators to identify the same animals in need of treatment and even combining them did not increase their predictive value of infection intensity or relative host damage from infection. The indicator sensitivity was influenced by the H. contortus isolate and sheep resistance phenotype in which they were tested. One isolate was poorly infective but induced high levels of anaemia (FAMACHA©) and diarrhea (DISCO) compared to the three others. The FAMACHA© and DISCO had higher values in the sheep group with a medium resistance phenotype (Blackbelly rams) indicating higher levels of damage compared to the high and low resistance phenotypes. We conclude that there is no 'one size fits all' approach to the use of indicators for Targeted Selective Treatment and the indicators should be calibrated to farm-specific conditions to increase their efficacy.

The heritability and specificity of responsiveness to infection with Haemonchus contortus in sheep.

High responder (HR) and low responder (LR) lines of sheep of the Hungarian Merino breed were selected by using faecal egg counts (epg) as parameter of responsiveness after double artificial Haemonchus contortus test infections. A total of 81 lambs born to assortative matings of HR rams with HR ewes and LR rams with LR ewes, as well as 28 control lambs from unselected parent sheep, were studied to estimate the heritability of responsiveness. A relatively high level of heritability (h2 = 0.49 +/- 0.17) was observed. A comparative assessment of responder classification carried out by two subsequent and distinct H. contortus and Trichostrongylus colubriformis infections revealed a remarkable degree of agreement: identical results in 69.7% and marginal differences in 23.2% of 99 animals. These results suggest that by selecting sheep for high responsiveness to a certain species of nematodes, one can also achieve a substantial improvement of resistance against a wide range of other nematode species.

Pathophysiology of Haemonchus placei infection in calves.

This study was conducted to investigate the pathophysiology of Haemonchus placei infection in Friesian calves. Seven calves were divided into two groups, three uninfected calves (control group) and four infected animals. The latter group were infected orally with 500 H. placei larvae kg-1 body weight. Five weeks after infection they were all housed in metabolic crates and injected with 125I-bovine albumin. 51Cr-red cells and 59Fe-transferrin, to study albumin metabolism, erythrokinetics and ferrokinetics. The results showed that there was a significant reduction in the mean haematocrit values and reduced weight gains in the infected calves compared with the controls. There was also a change in the distribution of albumin from the extravascular to the intravascular pool and a significant increase in the plasma and blood volumes of infected calves although the blood and albumin loss via the gastrointestinal tract recorded in this study was similar in both groups.

Haemonchus placei in calves: effects of dietary protein and multiple experimental infection on worm establishment and pathogenesis.

An experiment was conducted to examine the influence of dietary protein and immunisation on parasite establishment and pathogenesis of Haemonchus placei in calves. Four groups of 4-6-month-old worm-free calves (n = 4) were given a low protein diet (LP) containing 213 g crude protein (CP) per head per day or a high-protein diet (HP) containing 469 g per head per day CP. Five weeks later, calves in one of the two groups of each dietary treatment were given 50,000 H. placei infective larvae (L3). Twenty-five days later, infection in these groups was terminated by dosing with oxfendazole. This immunisation process was repeated 4 days later. Four days after termination of the second immunisation all calves were challenged with 100,000 L3. Five weeks later, all calves were slaughtered for abomasal worm counts. Worm establishment was lower in the immunised groups; however, only the HP-I group showed a significant reduction (P < 0.05). All calves gained weight during the first 13 week period, and after challenge the non-immunised groups lost weight, independent of the level of protein in the diet (P < 0.05). Packed cell volume values for all treatments only dropped after challenge (P < 0.05) and the HP-immunised group presented values significantly higher when compared with the other treatments. All calves were hypoproteinaemic and hypoalbuminaemic at the end of the experiment, regardless of the treatment. Immunised calves showed a normocytic normochromic anaemia, while the non-immunised groups presented a microcytic normochromic anaemia.

A comparison of the responses to repeated experimental infections with Haemonchus contortus among Scottish Blackface lambs.

Twenty helminth-naive Scottish Blackface lambs were given three infections with 10,000 infective larvae of Haemonchus contortus at 8 week intervals. An additional six lambs served as uninfected controls and eight lambs were infectivity controls. The lambs were 7 months old at the start of the infection. Four of the 20 lambs developed severe haemonchosis and were put down during the experiment. The remaining 16 lambs plus uninfected controls were necropsied 8 weeks after the third infection. The mean faecal egg count peaked 6-8 weeks after the first infection, gave a second smaller peak 6-8 weeks after the second infection but produced no peak after the third infection. Mean red blood cell counts fell rapidly during the first infection, then rose gradually during the second and third infections. The mean values suggested that two infections were sufficient to produce effective immunity in the sheep population but they masked considerable individual variation. Eleven animals appeared relatively resistant following the first infection, while two animals were relatively susceptible to even the third infection. The repeatability of mean faecal egg counts or mean red blood cell counts for each animal during the replicate infections were very high, because the rankings of the individual sheep remained remarkably stable. Faecal egg counts were very strongly correlated with red blood cell counts. Multiple regression analysis showed that four factors--faecal egg counts, red blood cell counts, weight and sex--accounted for essentially all of the observed variation in worm burdens among the lambs. Therefore, under these controlled experimental conditions, additional markers appear unnecessary for the detection of resistance status.

Resistance of four sheep breeds to natural and subsequent artificial Haemonchus contortus infection.

The response of Red Maasai sheep to natural and artificial Haemonchus contortus infections was compared with sheep of Blackheaded Somali, Dorper and Romney Marsh breeds. Significant breed differences in egg count, packed cell volume (PCV), and mortality rates showed that the Red Maasai sheep were more resistant to natural H. contortus infection than sheep from the other three breeds. Of the initial groups of 15 wethers of each breed, two animals from each of the Dorper and Blackheaded Somali groups and nine from the Romney Marsh group died with haemonchosis during a 12 month field study. Following artificial infection of the Red Maasai, Dorpers and Blackheaded Somalis, with 10000 H. contortus L3, the Red Maasai sheep maintained a lower egg output and a higher PCV than animals of the other two breeds. The results clearly showed that breed substitution with the Red Maasai is a control option in areas where sheep are kept for meat and H. contortus is endemic.

Response to artificial and subsequent natural infection with Haemonchus contortus in red Maasai and Dorper ewes.

Maiden Red Maasai and Dorper ewes were kept indoors and artificially infected with a single oral dose of 5000 infective larvae of Haemonchus contortus. Their faecal egg counts (FEC) and packed red cell volumes (PCV) were monitored for 9 weeks. They were then treated with an anthelmintic and turned out to graze together on a pasture contaminated with H. contortus. They grazed this pasture for 14 months and were allowed to mate and lamb. While at pasture the ewes were monitored for FEC, PCV and peripheral eosinophilia. Red Maasai ewes had significantly lower FEC, and for certain periods, significantly higher PCV and peripheral eosinophilia. During the periparturient period, FEC were about twice as high in the Dorper breed as the Red Maasai. These results confirm and extend previous reports on the superiority of the Red Maasai breed in East Africa.

Interaction of parasitism and nutrition and their effects on production and clinical parameters in goats.

Weaned wether goats (n = 144) approximately 6 months of age were placed in a 2 x 3 factorial design experiment for 5 months to test the main effects and interaction of two levels of nutrition (growth + maintenance, NUT1; twice growth + maintenance, NUT2) and three levels of Haemonchus contortus burden (0, 500 and 2000 larvae administered every 2 weeks: W0, W500 W2000, respectively) on weight, feed intake, level of infection and packed cell volume (PCV). The rationale for the experimental design was based on the lack of information concerning the interaction between nutritional status and worm burden. Results indicated significant effects of worm burden levels on PCV, faecal egg contents (eggs per gram of feces (EPG)), actual worm numbers, feed intake and efficiency of feed utilization. Nutrition x worm burden interactions were also significant for PCV and EPG. However, the differences detected for PCV and actual worm numbers did not translate into large or consistent differences in body weight. Goats on NUT2, after an initial period, showed little difference in body weight, irrespective of worm burden. Within the NUT1 level, W0 kids weighed more than W500 or W2000 kids throughout the study. Although not statistically significant, this constitutes a trend towards an interaction between nutrition and worm burden. In both nutrition levels, there were no body weight differences between W500 and W2000 until the last 14 days. Feed intake was depressed in the first 3 months of the experiment for infected animals, but was subsequently followed by a compensatory reaction. Lower establishment rates, based on actual worm counts, were observed for the higher infection level, but in both infection levels establishment rates tended to decrease with time. Nutrition was found to be more important to counteract the consequences of a parasitic infection than to counteract the establishment of that same infection.