Determining interaction between Duddingtonia flagrans and dietary lasalocid on in vitro recovery of Haemonchus contortus larvae

Authors: Rohila, Suman; Burke, Joan; VATTA, ADRIANO - Louisiana State University; MILLER, JAMES - Louisiana State University; BOWDRIDGE, SCOTT - West Virginia University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: A nematode trapping fungus, Duddingtonia flagrans (Df), fed to sheep is useful for biocontrol gastrointestinal nematodes on pasture. The objective was to determine interaction between Df and a common feed ingredient to prevent coccidiosis. In vitro methods determined that lasalocid, a coccidiostat, can be added to the diet in the presence of the commercially available Df, BioWorma without any interaction. The in vitro studies used showed the value of using water agar plates to culture fungus and larvae and reduces the number of animals needed for research studies. These results are important for farmers, feed coops, veterinarians, extension specialists, and scientists focused on controlling gastrointestinal nematodes in small ruminants.

Technical Abstract: Gastrointestinal nematodes (GIN), particularly Haemonchus contortus, are a major health issue for small ruminants due to high prevalence of anthelmintic resistance and its detriment to health and production. Spores of Duddingtonia flagrans (Df), a nematode-trapping fungus, are fed to livestock and pass through the digestive tract into the feces intact along with GIN eggs which subsequently hatch into larvae. In the feces, the fungus develops a network of loops and traps in response to presence of developing larvae, incapacitating them. It is important to know if common feed ingredients will interfere with the fungal activity. A study was conducted in Katahdin sheep to determine the interaction between D. flagrans and lasalocid, a feed additive for prevention of coccidiosis. Yearling rams (weighing 56.9 ± 4.3 kg) were dewormed (no eggs detected in feces) and randomly assigned to be fed 454 g/head of a corn/soybean mix without or with lasalocid (Purina® Restez® Sheep Balancer B136, 18.7 mg lasalocid/head; n = 4/diet) for 13 d before fecal collection. Within each dietary treatment, no Df or Df (60 mg/kg calculated to heaviest ram or 63 kg) was given in feed as BioWorma® (Int. Anim. Health Prod., Australia) 3 d before fecal collection. All feces were collected from rectum on the same day for coprocultures on water agar plates in two ratios of feces to larvae: 1) 5 g feces and 1000 larvae added on same day; 2) 2 g feces and 300 H. contortus larvae added 24 h later (n = 4 plates or reps/ram for each culture method; larvae were contaminated with Strongyloides spp. which were not counted as larvae initially or in larval recovery). Plates were cultured at 25°C for 8 d, then baermannized to recover live larvae which were then counted. Percent recovery was analyzed by Proc GLM in a 2 × 2 factorial (Df × lasalocid; SAS). In the 2 g plates, as expected, Df reduced larval recovery (P < 0.001), the presence of lasalocid slightly increased recovery (P = 0.05), and no interaction was detected. In the 5 g plates, Df reduced larval recovery (P = 0.001) and there was no effect of lasalocid or any interaction detected. In summary, BioWorma® for control of GIN should be able to be added to feed supplements with lasalocid without any impaired efficacy of Df in reducing larvae in feces.