A metagenomic approach was used to study the gut microbiome of Haemonchus contortus field strains and that of its predilection site, the abomasum of Dohne Merino sheep. The abomasum contents and H. contortus were collected from 10 naturally infected Dohne Merino sheep. The H. contortus specimens were classified and sexually differentiated using morphometric characters and was further confirmed through molecular identification. We investigated differences and similarities between the bacterial composition of the adult male and female H. contortus gut microbiomes, which were both dominated by bacteria from the Escherichia, Shigella, Vibrio and Halomonas genera. Major abundance variations were identified between the shared adult male and female H. contortus microbiomes. The results also revealed that Succiniclasticum, Rikenellaceae RC9 gut group and Candidatus Saccharimonas were the predominant genera in the Dohne Merino abomasum. This study provides insight into the highly diverse bacterial composition of the H. contortus gut microbiome and the Dohne Merino abomasum which needs to be studied further to explore the complex interactions of different gastrointestinal nematode microbiomes with the host.

Background and Aim: Previous studies recorded the prevalence of gastrointestinal nematodes (GIN) in Limpopo Province. However, the studies did not address the seasonal patterns of infection and did not cover all districts of Limpopo Province, namely; Capricorn, Sekhukhune, Waterberg, Mopani, and Vhembe. It is, therefore, important to provide up to date information on the prevalence and seasonal occurrence data of GIN in all districts of Limpopo province. The present study was conducted to determine the occurrence of anthelmintic resistance (AR) and document the prevalence of GIN infecting sheep in five districts of Limpopo Province, South Africa. Materials and Methods: Forty animals in each district were used for fecal egg count reduction test (FECRT) to determine AR against ivermectin (0.2 mg/kg), levamisole (LEV) (5 mg/kg), and albendazole (7.5 mg/kg). Egg hatch test (EHT) was used to determine AR against thiabendazole (TBZ) and micro-agar larval development test (MALDT) was used for both TBZ and LEV. Naturally, infected sheep (n=780) were sampled for prevalence across five districts of Limpopo. FAMACHA© eye-color score estimations were also performed for each study animal. Results: FECRT showed occurrence of AR in most of the districts and a few with suspected resistance. EHT results showed AR development against TBZ for all districts, while the MALDT showed no AR against LEV in all districts, but detected AR against TBZ in Sekhukhune, Capricorn, and Waterberg. Haemonchus contortus was the most resistant species. A high nematode prevalence (88-100%) and 1210-1861 eggs per gram (EPG) was observed in all districts during the hot wet season, decreasing to 75-80% (453-1202 EPG) during the cold dry season. The sheep revealed a FAMACHA© mean score of 3, indicating mild anemia during the hot wet season except for Vhembe district that revealed a FAMACHA© mean score of 4 during the hot wet season, indicating anemia. Conclusion: AR recorded in Limpopo Province may be due to under-dosing caused by lack of weighing equipment and high treatment frequencies due to lack of proper training on anthelmintic use. The detection of AR in Limpopo is an important finding because it will help in outlining effective management systems against GIN.

For decades anthelmintics have been used as the primary control measure for worm infections in livestock. However, there has been continuous development of anthelmintic resistance (AR) by the parasitic worms infecting livestock. This chapter reviews AR in livestock with a special focus on treatment and control, modes of action of different anthelmintic classes, risk factors leading to development of AR, conventional and molecular tools used to detect AR, FAMACHA© and holistic control strategy to control anthelmintic resistance.

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