Relative resistance of Menz and Washera sheep breeds to artificial infection with Haemonchus contortus in the highlands of Ethiopia

Factors influencing regional epidemiology of strongyle nematodes at organized sheep farms in Rajasthan

A study was conducted to observe the influence of year, season, month, breed, age and sex on epidemiology of strongyle nematodes in different sheep breeds managed at organised farms in arid and semi-arid Rajasthan by evaluating 14,030 fresh faecal samples (from April 2016 to March 2019). The overall incidence of strongyle worms was significantly higher (74.1%) in semi-arid as compared to 27.4% in arid region. Among breeds, it varied from 25.6% in Magra to 74.8% in Malpura sheep. The effect of year was significant on regional as well breed-wise incidence. Season had significant effect on regional incidence with maximum incidence during monsoon. A significant breed variation in overall and seasonal incidence was found only in arid region. Irrespective of sheep breed, significantly higher incidence of strongyle worms was observed in adult sheep in both the regions. Male had significantly higher incidence of strongyle worms in both the regions. The effect of agro-climatic region was significant on overall intensity of strongyle worms with mean FECs of 117.8±3.7 epg in arid and 1098.9±45.2 epg in semi-arid region. Breed-wise, the effect of year on intensity of strongyle nematodes was significant in arid region only. Seasonal intensity was significantly higher during monsoon season in both the agro-climatic regions and in all the breeds. Effect of age on overall intensity of infection was also significant in both the regions with higher mean FECs in adult animals as compared to young ones. In both the regions, males possessed higher FECs as compared to females. On coproculture, Haemonchus contortus, Trichostrongylus sp and Oesophagostomum sp were recovered with maximum (71.1±2.1%) mean annual proportion of H. contortus. Availability of infective larvae of GI nematodes on herbage was observed during monsoon and extended up to post-monsoon season in semi-arid region. Comparatively higher herbage infectivity was not noticed in semi-arid farm with a peak of 2,100.0±97.9 L3/kg dry matter of herbage in September. The study suggest a marked influence of agro-climatic region on epidemiology and dynamics of strongyle nematodes in sheep flocks and on pasture. The breed variation was evident only in arid conditions. Further, the magnitude of monthly intensity of strongyle infection in arid region suggested anthelmintics intervention through targeted selective approach instead of strategic en-mass drench.

Individual variability among autochthonous sheep in Northern Tunisia to infection by abomasum nematodes and Babesia/Theileria parasites

In Tunisia, livestock plays an important role in the economy; unfortunately, Tunisian sheep population faces several health challenges. The aim of this trial was to study phenotypic variability of four local sheep breeds and strains to abomasum nematodes infection and to Babesia/Theileria parasites. Faeces, blood and abomasum contents were collected from 310 sheep slaughtered in eight commercial slaughterhouses across North Tunisia. Haematological and biochemical parameters were assessed. DNA was extracted and catch‐all primers were used to detect both Theileria spp. and Babesia spp. DNA. Faecal egg counts (FEC) was quantitatively assessed using simple flotation technique followed by McMaster technique. Male and female worms were collected from all abomasum contents and counted under a stereomicroscope. The percentage of faeces samples positive for GIN’s eggs was 30.82%. After worms’ recovery, the infection prevalence was estimated to 75.90%. The overall infection prevalence by Babesia spp. and Theileria spp. was 4.21%. The dispersion of observations plots obtained by principal component analysis (PCA) showed two clusters of individuals. The first cluster contains animals having positive Babesia/Theileria PCR, presence of nematodes in the abomasum contents and relatively low total worm count (TWC < 500) expect one animal which was found bearing high TWC (>500). In this same group, with a suspected form of resistance, animals showed normal values of albumin and normal haematological parameters (red blood cell count [RBC], haemoglobin [Hb] and packed cell volume [PCV]). The second cluster represents all the other observations in which subgroups of animals were distinguished on the basis of their potential resistance to abomasum nematodes. Multiple correlations showed significant positive correlations between RBC/Hb, RBC/PCV, PCV/Hb and FEC/TWC. Significant negative correlations were observed between TWC/RBC and TWC/Hb. It is concluded that the phenotypic variability among local sheep breeds is essential for more advanced genetic and genomic studies.

Evaluation of the in vivo anthelmintic properties of Mitragyna inermis (Willd.) as a livestock dewormer against parasitic hematophagous worm Haemonchus contortus infections in different breeds of lambs

Gastrointestinal (GI) nematodes remain a major constraint on livestock production throughout the world. This study assessed the in vivo efficacy of the powder of Mitragyna inermis leaves in three breeds of lambs, namely, West African dwarf lambs (WAD), West African long-legged lambs (WALL), and F1 lambs (cross of a WALL ram with a WAD ewe), artificially infected with 3000 L3s of Haemonchus contortus in a controlled experiment. Fecal sample examination, serological analysis, and necropsy were carried out to determine the egg count, worm burden, and worm fecundity reduction. A dose of 3.2 g/kg body weight (BW) M. inermis was administered per the oral route for three consecutive days and repeated 2 weeks later. Compared with the control, the powder of M. inermis leaves (> 60%) and albendazole (100%) significantly reduced (p < 0.01) fecal egg counts (FECs) in the three breeds of lambs. The posttreatment reduction in FECs fluctuated from 56.99 to 78.75% for WAD lambs, 38.39 to 66.39% for WALL lambs, and 35.55 to 63.11% for F1 lambs (WALL × WAD). Significant differences (p < 0.05) were observed in packed cell volume values before and after infection. M. inermis reduced the egg-laying capacity of female adult worms by up to 60% and eliminated more than 80% of the adult worms of H. contortus in lambs. Furthermore, albendazole reduced the worm count and fecundity of female worms by greater amounts than M. inermis (100%). The findings of this study showed that M. inermis is a good source of bioactive compounds for drug development. According to this result, a 3.2 g/kg BW dose of the plant could be applied for the control of GI nematodes in small ruminants.

Predicting the effects of parasite co-infection across species boundaries

It is normal for hosts to be co-infected by parasites. Interactions among co-infecting species can have profound consequences, including changing parasite transmission dynamics, altering disease severity and confounding attempts at parasite control. Despite the importance of co-infection, there is currently no way to predict how different parasite species may interact with one another, nor the consequences of those interactions. Here, we demonstrate a method that enables such prediction by identifying two nematode parasite groups based on taxonomy and characteristics of the parasitological niche. From an understanding of the interactions between the two defined groups in one host system (wild rabbits), we predict how two different nematode species, from the same defined groups, will interact in co-infections in a different host system (sheep), and then we test this experimentally. We show that, as predicted, in co-infections, the blood-feeding nematode Haemonchus contortus suppresses aspects of the sheep immune response, thereby facilitating the establishment and/or survival of the nematode Trichostrongylus colubriformis; and that the T. colubriformis-induced immune response negatively affects H. contortus This work is, to our knowledge, the first to use empirical data from one host system to successfully predict the specific outcome of a different co-infection in a second host species. The study therefore takes the first step in defining a practical framework for predicting interspecific parasite interactions in other animal systems.

Responses of Sri Lankan indigenous goats and their Jamnapari crosses to artificial challenge with Haemonchus contortus

Goat farming plays an important role in the Sri Lankan rural economy. Sri Lankan indigenous (SLI) goats and their crossbreds are reared mainly under extensive management and indiscriminately exposed to pathogens and parasites. This study was designed to evaluate resistance to haemonchosis in SLI goats and their Jamnapari crossbreds (JCB) in the dry zone of Sri Lanka. Twenty SLI and 20 JCB 4-month-old male goats were artificially challenged with 5000 H. contortus L₃ larvae_. Faecal egg counts (FEC), body weights, FAffa MAlan CHArt (FAMACHA®) scores, packed cell volumes (PCV), red blood cell counts, total and differential white blood cell counts, blood haemoglobin contents, serum total protein and albumin contents, and serum pepsinogen and antibody levels were determined at 0, 21, 28, 35 and 42days after challenge. Effects of measurement time were significant for all variables (P<0.05). Breed effects approached significance (P=0.06) and measurement time×breed interaction was significant (P<0.05) for FEC. Peak FEC occurred at day 35 in both goat types, and JCB goats had higher FEC than SLI goats at days 28 (P<0.001), 35 (P<0.10), and 42 (P<0.10). Means for FEC at day 35 were 1783±446 eggs per gram of feces (epg) for SLI kids and 3329±850 epg for JCB kids. Haematological parameters, serum chemistry, and FAMACHA scores suggested that SLI goats were recovering from parasitic infection by day 42, whereas JCB goats had increasing severity of anaemia. Means for PCV in SLI goats decreased from 26.8±0.7% at day 0 to 19.7±0.9% at day 35 and thereafter increased to 20.2±0.9% at day 42. Means for PCV in JCB goats declined from 25.9±0.6% at day 0 to 17.2±0.9% at day 42. Eosinophilia was observed in both genotypes. The JCB goats were heavier than SLI goats and had higher antibody titres, reflecting higher levels of parasitism. Both goat types significantly increased in body weight during the experiment and therefore tolerated parasite infection without severe production losses. We concluded that SLI goats were more resistant to haemonchosis than JCB goats, but that JCB goats were somewhat resilient to parasitic infection. Substantial variability in measurements associated with parasite infection in both breeds indicated potential to improve parasite resistance. Phenotypic information should be coupled with genomic information to identify appropriate breeding goals for future selection programs.

Genetic Diversity and Population Structure of Ethiopian Sheep Populations Revealed by High-Density SNP Markers

Sheep in Ethiopia are adapted to a wide range of environments, including extreme habitats. Elucidating their genetic diversity is critical for improving breeding strategies and mapping quantitative trait loci associated with productivity. To this end, the present study investigated the genetic diversity and population structure of five Ethiopian sheep populations exhibiting distinct phenotypes and sampled from distinct production environments, including arid lowlands and highlands. To investigate the genetic relationships in greater detail and infer population structure of Ethiopian sheep breeds at the continental and global levels, we analyzed genotypic data of selected sheep breeds from the Ovine SNP50K HapMap dataset. All Ethiopian sheep samples were genotyped with Ovine Infinium HD SNP BeadChip (600K). Mean genetic diversity ranged from 0.29 in Arsi-Bale to 0.32 in Menz sheep, while estimates of genetic differentiation among populations ranged from 0.02 to 0.07, indicating low to moderate differentiation. An analysis of molecular variance revealed that 94.62 and 5.38% of the genetic variation was attributable to differences within and among populations, respectively. Our population structure analysis revealed clustering of five Ethiopian sheep populations according to tail phenotype and geographic origin-i.e., short fat-tailed (very cool high-altitude), long fat-tailed (mid to high-altitude), and fat-rumped (arid low-altitude), with clear evidence of admixture between long fat-tailed populations. North African sheep breeds showed higher levels of within-breed diversity, but were less differentiated than breeds from Eastern and Southern Africa. When African breeds were grouped according to geographic origin (North, South, and East), statistically significant differences were detected among groups (regions). A comparison of population structure between Ethiopian and global sheep breeds showed that fat-tailed breeds from Eastern and Southern Africa clustered together, suggesting that these breeds were introduced to the African continent via the Horn and migrated further south.

Between-breed variations in resistance/resilience to gastrointestinal nematodes among indigenous goat breeds in Uganda

Gastrointestinal nematodes (GINs), Haemonchus contortus, are a major health problem in goat production. Resistance to H. contortus, the most prevalent GIN in Uganda, was studied among three indigenous goat breeds to assess their differences. Twelve male goats of each breed approximately 7 months old of small East African (SEA), Mubende, and Kigezi goats from smallholder farmers in Arua, Mubende, and Kabale were assembled for the study. At the station, they were dewormed with a combination therapy of the broad-spectrum dewormers closantel and albendazole to free the goats of gastrointestinal parasites. During experimentation, the goats were kept indoors and ad libitum fed on clean banana peels and napier grass. On attainment of zero-worm-egg status, the goats were artificially infected with 18,000 third-stage (L3) larvae of H. contortus prepared according to Baermann’s procedure. Data were collected on fecal egg count (FEC), packed cell volume (PCV), and body weight (BW) on a 2-week basis until 12 weeks post infection and carcass weight and total worm count (WC) in the abomasum at termination of the experiment. The data on FEC, PCV, and BW were subjected to repeated-measure analysis of variance and the others by one-way analysis of variance. FEC between breeds was only significantly different at 12 weeks post infection (p = 0.04). Generally, higher FEC was recorded in Kigezi compared to SEA and Mubende goats. Carcass weight was significantly different among breeds (p < 0.05), with Mubende having the highest carcass weight, followed by Kigezi and SEA. PCV and daily weight gains were significantly different between breeds (p < 0.05). WC was not significantly different between the breeds. FEC and PCV were weakly significant at later stages of the experiment with higher parasite burden suggesting potential variation in resistance to H. contortus. These differences could be exploited in designing breeding programs with disease resistance in indigenous goat breeds.

Resistance to gastrointestinal parasite infection in Djallonké sheep

Gastrointestinal parasitism places serious constraints on small ruminant production. The situation has been exacerbated by development of drug resistance in many parasite populations, leading to interest in identification of animals with genetically mediated resistance or tolerance to nematode infections. This study assessed the response to natural infection with gastrointestinal nematodes (GIN) in Djallonké sheep during the rainy season in the Sudan-Guinea Savannah region of Burkina Faso. Haemonchus contortus is the most prevalent GIN at this site and time. Djallonké lambs (n=434) were sampled from 40 households and evaluated at a common location in southern Burkina Faso. Lambs were dewormed with levamisole at 2 to 6 months of age and returned to infected pastures. Fecal egg counts (FEC), packed cell volumes (PCV), and FAffa Malan CHArt (FAMACHA©) scores were determined 28 and 35 days after deworming. Lamb mortality was monitored throughout the experiment. Least-squares means for BW increased from 13.8±0.2 kg at 28 days to 14.0±0.2 kg at 35 days (P<0.01). Simple means and medians for FEC were 615 and 100, respectively, at 28 days and 850 and 175, respectively, at 35 days. The FEC exhibited strong right skewness. Following logarithmic transformation and back-transformation of resulting least-squares means to the original scale, FEC were higher (P<0.01) for males (208±27) than females (122±10). Least-squares means for PCV decreased (P<0.001) from 28 (36.3±0.5%) to 35 days (33.7±0.5%), and were higher (P<0.01) for females (36.0±0.4%) than males (33.9±0.7%). Correlations (r) between repeated measurements of BW, FEC, PCV and FAMACHA scores at 28 and 35 days were all positive (P<0.001). The correlation between FAMACHA scores and PCV was negative at 28 (r=-0.14) and 35 days (r=-0.18) (P<0.001). This study revealed that BW was an easily measured predictor of the ability of the lamb to resist infection with GIN and maintain PCV, and confirmed that FAMACHA scores are useful indicators of differences in FEC. Approximately 40% of female and 30% of male lambs did not show detectable levels of infection (i.e. FEC=0) under field conditions. The great variability that was observed in FEC and PCV suggests potential to use Djallonké sheep in breeding programs to enhance resistance to GIN.

Effect of the infection with the nematode <i>Haemonchus contortus</i> (Strongylida: Trichostrongylidae) on the haematological, biochemical, clinical and reproductive traits in rams

This study aimed to investigate the effect of Haemonchus contortus infection on rams’ haematological, biochemical and clinical parameters and reproductive performances. A total number of 12 Barbarine rams (control and infected) were included in the experiment. The infected group received 30 000 H. contortus third-stage larvae orally. Each ram’s ejaculate was immediately evaluated for volume, sperm cell concentration and mortality rate. At the end of the experiment (day 82 post-infection), which lasted 89 days, serial blood samples were collected in order to assess plasma testosterone and luteinising hormone (LH) concentrations. There was an effect of time, infection and their interaction on haematological parameters (p < 0.001). In infected rams, haematocrit, red blood cell count and haemoglobin started to decrease from 21 days post-infection. There was an effect of time and infection for albumin. For total protein, only infection had a statistically significant effect. For glucose, only time had a statistically significant effect. Concentrations were significantly lower in infected rams compared to control animals. A significant effect of infection and time on sperm concentrations and sperm mortality was observed. The effect of infection appears in time for sperm concentrations at days 69 and 76 post-infection. Sperm mortality rate was significantly higher in infected animals at day 46 post-infection when compared to control group (p < 0.05). Finally, plasma testosterone traits (average concentration, cumulated levels during the sampling period and pulse frequency) were depressed in infected rams when compared to control counterparts; none of these endocrine traits were affected for plasma LH.