The effect of season upon the life cycle and development of Haemonchus contortus in experimentally infected lambs

View the project final report

Commodities

• Animals: goats, sheep

Practices

• Animal Production: animal protection and health, parasite control

Globally, small ruminant producers face economic losses due to the prevalence of gastrointestinal nematode infections (GIN), particularly the most pathogenic GIN, Haemonchus contortus. It has been found that plant secondary compounds have an anti-parasitic effect on small ruminant GIN infections as assessed primarily through in vitro assays and feeding trials. Although it is known that H. contortus larvae arrest their development within the host during the winter months, it is unknown how season or age of the adult worm affects the viability of eggs deposited in the manure or the efficiency with which the resulting larvae artificially exsheath in vitro or in vivo within the rumen. The objective of this study is to determine the role of season and age of adult H. contortus on hatchability of their eggs and ability of resulting infective larvae to exsheath artificially in vitro or in vivo within the rumen. Two donor lambs will be experimentally infected at the beginning of each season (September 22, December 21, 2017 and March 20, and June 21, 2018). Feces will be collected once a month for six months. Eggs will be harvested from the feces and hatchability tested. The fecal matter will be cultured and the resulting infective larvae will be subjected to two in vitro exsheathment assays as well as in vivo using ruminally fistulated ewes. The results of this experiment will increase our understanding of the lifecycle of H. contortus and will ultimately improve current recommendations for the control of these parasites.

The main objective of this project is to elucidate factors affecting the viability of H. contortus eggs and larvae from adult worms residing within the host animal (sheep and goats). I hypothesize that larval viability will be significantly lower when infection is developing in colder vs. hotter temperatures. I also hypothesize that no significant differences will be observed for egg hatchability according to age of infection. This study can lead to new discoveries and broaden our understanding of H. contortus life cycle in relation to sensitivity to environmental season and temperature, as well as length of infection within the host.
Objectives:
1. To determine if age of the adult worm in the host animal affects the ability of the egg to hatch as well as viability and exsheathment of the resulting third stage H. contortus larvae.
2. To determine the effect of season on the adult worm in the host animal and the ability of the eggs from these worms to hatch at varying times of year as well as viability and exsheathment of the resulting L3 H. contortus larvae.
3. Correlate two common artificial in vitro exsheathment methods (CO2 and bleach) to in vivo exsheathment using ruminally fistulated ewes.