Hypobiosis of Haemonchus contortus in natural infections of sheep and goats in a semi-arid area of Kenya

A comparative study on clinical pathology changes in experimentally infected sheep with active and arrested larvae of Haemonchus contortus

“…The abomasal contents and mucosal scraps were collected. Abomasum walls were immersed in artificial gastric juice for recovery of immature worms (Gatongi et al 1998). Adult worms and larvae were separated and counted according to the Baermann method.…”

“…The infective larva of nematodes is sensitive to winter conditions, therefore larvae undergo an arrested form and complete their growth during spring (Gatongi et al 1998;Sargison et al 2007). This phenomenon is well-known in parasitic nematodes of ruminants, particularly in species of the subfamily Ostertagiinae and the genus Haemonchus (Eysker 1980;Gasser et al 2008).…”

Does the blood-sucking nematode Ashworthius sidemi (Trichostrongylidae) cause deterioration of blood parameters in European bison (Bison bonasus)?

“…It is also known that the high infection rate of pathogenic blood-sucking nematodes depends on management practices such as supplementary feeding in winter (Kołodziej-Sobocińska et al unpublished data). Studies by Gatongi et al (1998) on the blood-sucking nematode Haemonchus contortus revealed that high infection rates caused by extensive use of pastures by sheep results in life-threatening levels of anaemia and an associated potential for significant reductions in lamb survival. As a result, to avoid the consequences of nematode infections in ruminant livestock, sustainable nematode parasite control strategies are used such as grazing management and biological control (Waller 2006).…”

Trends and challenges in the effective and sustainable control ofHaemonchus contortusinfection in sheep. Review

“…However, in extreme degrees of temperatures and relative humidity, the L4 stage may enter into a phase of arrested development or hypobiosis (Reinecke, 1989;Urquhart et al, 1996, Miller et al, 1998. Hypobiosis usually follows the onset of cold autumn/winter conditions in the northern hemisphere (Waller et al, 2004) or very dry conditions in the subtropics and tropics (Gatongi et a., 1998). This might be an environmental stimulus received by the free-living infective stages prior to ingestion by the host, or it could be an evolutionary parasitic adaptation to avoid adverse climatic conditions for survival of the freeliving stages by a significant number of parasites remaining as sexually immature stages in the host until more favourable conditions return.…”

“…importance of haemonchosis may be explained by: the parasite's ability to produce large numbers of eggs, which results in extensive pasture contamination; the blood-sucking nature of the nematode that causes variable degrees of anaemia, loss of production and mortality in lambs and kids in situations where few or no control measures are used; and its ability to survive adverse climatic conditions through hypobiosis (Gatongi et al, 1998;Waller et al, 2004). The nature of the parasite, host genetic and physiological factors, as well as environmental determinants, greatly influence the degree of infestation and thus appropriate control strategies.…”