Lassoing worms of exotic ruminant hoofstock in zoos
James E. Miller
Professor of Veterinary Medicine
Louisiana State University
Since my last Timely Topic, there has been some exciting work done at zoos to evaluate the nematode-trapping fungus, Duddingtonia flagrans, in exotic ruminant hoofstock as a means to reduce exhibit forage infective larval levels. The exotics included giraffe, roan/sable/pronghorn antelope, gerenuk and transcaspian urial.
These are high-risk species based on previous epidemiological work. The zoo dilemma is that exotic ruminants brought into captive, somewhat un-natural environment exhibits (small to more expansive) are exposed to parasitism at much higher levels than their counterparts residing in their native environments due to higher stocking rates, irrigation of vegetation, stress from captivity, insufficient nutrition, inability to close/rest exhibits and lack of browse (browsers become grazers).
The parasite problem resulted in reliance on traditional anthelmintics used in the domestic ruminant industry for control. Eventually, anthelmintic resistance became a problem due to frequent treatments, varying compliance of orally administered products, inaccurate estimated body weights and unknown drug metabolism issues.
As a refresher on how this fungus works, see the December 2013 Timely Topic. Briefly, fungal spores are mixed in animal feed and pass through the gut into the feces. The spores germinate and form hyphal nets/loops. Worm larvae that hatch from eggs get trapped in these loops and die. Therefore, fewer larvae end up on pasture for animal consumption. For these studies, spores were mixed (daily) in supplement feed at a dose of 30,000 spores per kg of body weight.
Results of larval recovery from feces indicated that the number of larvae was reduced by over 80% as long as the spores were fed for periods ranging from 2-9 weeks. These results support the potential of Duddingtonia flagrans to control worm larvae in
the feces and would be a useful tool in control programs aiming to decrease worm infection over time.
But don’t forget that this needs to be used in combination with proper exhibit (farm) management, proper animal management, parasite monitoring programs, other non-chemical alternatives (such as COWP and condensed tannin plants, i.e. serecia lespedeza, etc.) and smart use of anthelmintics. What was learned here can also be applicable to small ruminant worm control.
Some good news is that the Australian company that is making this product (International Animal Health Products) is in the final stages of working with our federal agencies on getting it registered for marketing in the US for zoos and small ruminants.