Date of Award

Summer 8-16-2024

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Anne Lichtenwalner

Second Committee Member

Debra Kantor

Third Committee Member

Pauline Kamath

Additional Committee Members

Amber Roth

Jim Weber

Abstract

An animal health challenge that many small ruminant producers face is the impact of parasites on production, such as weight loss, reproductive problems, and product yield. The nematode, Parelaphostrongylus tenuis (meningeal worm) can cause severe neurologic symptoms and death in small ruminants. This “phantom parasite” does not have a premortem diagnostic test to detect it, thus the level of incidence in livestock is unknown. Because of this, prevention is the best option to limit incidence, though no research on P. tenuis risk factors to livestock naturally on grazing pastures has been explored. This work aimed to investigate the transmission risk factors of P. tenuis through the intermediate hosts, terrestrial gastropods (snails and slugs) and to explore methods of mitigating risk on a pasture-wide scale.

Over two years, collections and surveys of gastropods were held on six small ruminant farms. This study found that 1% of gastropods living on pastures carry P. tenuis. An in-depth analysis of gastropod intermediate hosts showed a variety of helminths in addition to P. tenuis, including Muellerius capillaris or sheep/ goat lungworm. Snail characteristics, such as shell size, and seasonality on the pasture were correlated with P. tenuis larvae in infected snails.

To investigate methods of controlling high abundances of gastropods on pasture, an integrated pest management approach was explored through an on-farm case study. Pastured poultry, using chickens, and mowing were both found to be successful practices for mitigating snail populations on pastures. However, in plots intentionally allowed to regrow, snail populations quickly rebounded, suggesting that mowing is a practice that may need to be maintained to be effective.

The knowledge, attitudes, and management practices were examined by stakeholders to determine risk perceptions of P. tenuis and other parasites. The farmers involved with this study and veterinarians reported changes in knowledge after learning about study results, and voiced challenges and needs based around animal health education and information gathering.

These data provide insight into the factors of risk and risk-reduction of P. tenuis to small ruminants on grazing space. Farmers and managers may consider these practical methods for animal health improvement and prevention.

Download

Share