New paraprobiotic-based treatment for control of the barber pole worm Haemonchus contortus in sheep

Authors: SANDERS, JOHN - Virginia Tech; XIE, YUE - Non ARS Employee; GAZZOLA, DAVID - University Of Massachusetts, Amherst; LI, HANCHEN - University Of Massachusetts, Amherst; ABRAHAM, AMBILY - University Of Massachusetts, Amherst; FLANAGAN, KELLY - University Of Massachusetts, Amherst; RUS, FLORENTINA - University Of Massachusetts, Amherst; MILLER, MELANIE - University Of California, San Diego; HU, YAN - University Of Massachusetts, Amherst; Zarlenga, Dante; Li, Robert; Urban, Joseph; OSTROFF, GARY - University Of Massachusetts, Amherst; ZAJAC, ANNE - Virginia Tech; AROIAN, RAFFI - University Of Massachusetts, Amherst

Submitted to: International Journal for Parasitology: Drugs and Drug Resistance
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2020
Publication Date: 11/19/2020
Citation: Sanders, J., Xie, Y., Gazzola, D., Li, H., Abraham, A., Flanagan, K., Rus, F., Miller, M., Hu, Y., Zarlenga, D.S., Li, R.W., Urban Jr, J.F., Ostroff, G., Zajac, A., Aroian, R.V. 2020. New paraprobiotic-based treatment for control of the barber pole worm Haemonchus contortus in sheep. International Journal for Parasitology: Drug and Drug Resistance. 14(230-236). https://doi.org/10.1016/j.ijpddr.2020.11.004.
DOI: https://doi.org/10.1016/j.ijpddr.2020.11.004

Interpretive Summary: Parasitic nematodes (worms) that infect livestock reduce production of meat, milk and fiber. Haemonchus contortus is an abomasal species that can cause severe dehydration, weight loss, lethargy, rough hair coats, poor wool/milk/meat production, submandibular edema, anemia, and death in heavily infected individuals. Lambs and kids are at the greatest risk of developing disease due to their immature immune response and high infection from environmental contamination from infected ewes. We have shown that the nematode-intoxicating crystal (Cry) protein Cry5B, made by the soil bacterium Bacillus thuringiensis (Bt), has broad in vivo anthelmintic properties against parasitic nematodes in monogastric animals (mice, hamsters, dogs, and pigs. Furthermore, Bt Cry proteins related to Cry5B are used safely, globally, and extensively as the number one biological insecticide agent in the world. The three-domain Cry proteins are pore-forming proteins that specifically bind to and disrupt the integrity of the invertebrate gut but the receptor is not found in vertebrates. We tested the efficacy of Cry5B specifically against H. contortus. Cry5B was tested in cultures in a larval development assay and against an adult strain of H. contortus resistant to three classes of anthelmintics (triple anthelmintic resistant), and then recombinant Cry5B spore-crystal lysates were tested against an experimental H. contortus infection in goats. Based on the results of these studies, a new Active Pharmaceutical Ingredient containing Cry5B called Inactivated Bactetrium with Cytosolic Crystal (IBaCC, a paraprobiotic) was developed and used to treat sheep experimentally infected with H. contortus. The results of these studies showed that Cry5B has excellent potential to positively impact sheep health and productivity by significantly eliminating H. contortus adult worm infection and the epidemiology of transmission by reducing egg production. The work strongly supports the need for more investigation of this new class of anthelmintics for use in other ruminant species and in humans.

Technical Abstract: Haemonchus contortus is a critical parasite of small ruminants such as goats and sheep. Infection by this blood-feeding gastrointestinal nematode (GIN) parasite has significant health consequences on sheep that are potentially dire on lambs and kids. The parasite has developed resistance to virtually all known small molecule anthelmintic drug classes used to treat it, giving rise in some areas to multi-drug resistant parasites that are very difficult to control. Thus, new anthelmintic de-wormers are urgently needed. Bacillus thuringiensis crystal protein 5B (Cry5B), a naturally occurring protein made by a bacterium widely and safely used around the world as an insecticide, represents a new non-small molecule modality for treating GINS. Cry5B has demonstrated anthelmintic activity against parasites related to those that infect humans and monogastric animals but has not yet been studied in ruminants. Here we show that H. contortus adults are susceptible to Cry5B protein in vitro. A study using Cry5B, produced in its natural form as a spore-crystal lysate, against H. contortus infection in goats had no significant efficacy. However, a new Active Pharmaceutical Ingredient (API) paraprobiotic form of Cry5B called IBaCC, in which Cry5B crystals are encapsulated in dead Bt bacilli, showed excellent efficacy against larval stages of H. contortus and protein stability in cow rumen fluid. When given to sheep experimentally infected with H. contortus as three 60 mg/kg doses, Cry5B IBaCC resulted in significant reductions in fecal egg counts (90%) and parasite burdens (72%), with a very high impact on female parasites (96% reduction). These data indicated that Cry5B IBaCC is a potent new treatment tool for small ruminants in the battle against H. contortus.