Haemonchosis in Sheep and Goats, Control Strategies and Development of Vaccines against Haemonchus contortus

Abstract

The evolutionary success of parasitic worms causes significant economic losses and animal health problems, including in the small ruminant industry. The hematophagous nematode Haemonchus contortus is a common endoparasite that infects wild and domestic ruminants worldwide, especially in tropical and subtropical regions. To date, the most commonly applied control strategy is the administration of anthelminthic drugs. The main disadvantages of these chemicals are their ecotoxic effects, the necessary withdrawal period (especially important in dairy animals) and the increasing development of resistance. Vaccines offer an attractive alternative control strategy against Haemonchus infections. In previous years, several potential vaccine antigens prepared from H. contortus using the latest technologies have been assessed in clinical trials using different methods and strategies. This review highlights the current state of knowledge on anti-H. contortus vaccines (covering native, recombinant and DNA-based vaccines), including an evaluation, as well a discussion of the challenges and achievements in developing protective, efficient, and long-lasting vaccines to control H. contortus infection and haemonchosis in small ruminants. This paper also addresses novel developments tackling the challenge of glycosylation of putative candidates in recombinant form.

First evaluation and detection of ivermectin resistance in gastrointestinal nematodes of sheep and goats in South Darfur, Sudan

“…were detected in larval cultures after treatment. Haemonchus contortus in small ruminants is ranked first among different ruminant nematodes to evolve resistance against the available anthelmintics [3, 63], which has been attributed to its very high reproductive potential which resulted in huge population sizes [64]. The findings from natural infections in sheep and goats were confirmed in experimental infections using L3 cultured from eggs extracted from mature gravid female H. contortus goats from Kass and Nyala and used to infect worm-free goats.…”

“…Due to blood losses during feeding and continuous bleeding at previous attachment sites, anaemia, hypoproteinaemia, oedema and loss of animal live-weight are frequently observed clinical signs [4]. Infected animals also tend to have a reduced digestive capacity which affects the uptake of nitrogen, organic matter and energy, and death may occur in heavily infected young animals [3].…”

“…In livestock, gastrointestinal nematodes (GINs) are causing significant losses in production. The strongest pathogenic effects in ruminants are due to infection with Haemonchus spp., haematophagous parasites in the abomasum [3]. Haemonchus contortus is an economically important parasite of small ruminants, and it causes serious problems in both extensive and intensive small ruminant farming systems in warm to moderate climatic regions.…”

“…Due to blood losses during feeding and continuous bleeding at previous attachment sites, anaemia, hypoproteinaemia, oedema and loss of animal live-weight are frequently observed clinical signs [4]. Infected animals also tend to have a reduced digestive capacity which affects the uptake of nitrogen, organic matter and energy, and death may occur in heavily infected young animals [3]. Other GIN genera are also described as pathogenic and causing significant production losses in sheep and goats, including the genera Teladorsagia , Cooperia , Trichostrongylus , Chabertia , Oesophagostomum and Nematodirus [5].…”

Epidemiology and phylogeny of Haemonchus contortus through internal transcribed spacer 2 gene in small ruminants

“…Our findings concur with those of ( 38 , 62–64 ), as they also noted a higher H. contortus infection rate in the younger and older age groups. Higher infection rates in the younger and older age groups could be associated with reduced immunity in these animals since most cases of haemonchosis afflict either immunocompromised adults or non-immune young animals (i.e., during the first grazing season) ( 65 ).…”