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Nematode © Christian SLAGMULDER

Anti-parasitic drugs: humans and animals united in the same fight

By Pascale Mollier and Delphine Achour, translated by Inge Laino
Updated on 06/20/2017
Published on 12/07/2015

Intestinal, pulmonary and cutaneous parasites plague both humans and animals. The 2015 Nobel Prize for Medicine rewarded the development of new medicines to fight parasites in man, while INRA and the French national veterinary school in Toulouse have joined forces to find solutions for animal health. Their work is a shining example of the “One Health” initiative: one medicine, one health for all.

In a poignant reminder of how high the stakes are for public health and animal health in the fight against parasitic diseases, the 2015 Nobel Prize for Medicine was attributed to scientists who are developing anti-parasitic drugs(1). For example, a class of compounds called avermectins are used to treat parasitic diseases such as river blindness and lymphatic filariasis, which affect some 150 million people around the world. Interestingly, avermectins were originally developed to fight intestinal, pulmonary and cutaneous parasites in farm animals. The history of these drugs are a perfect example of the “One Health” initiative: “one medicine, one health for all”, referring to the inextricable link between human and animal health.

Since avermectins came to market in the 1980s, INRA and the French national veterinary school in Toulouse (ENVT) have made significant strides in understanding the drug’s mechanisms of action and reasoned use in farm animals. Experiments have been carried out on cows, goat, sheep, and horses, but also on more exotic species such as camel and zebus, as well as household pets.
Since 1980, more than 200 articles have been published on the subject in peer-reviewed journals. This report presents the principle findings of research.
 
(1) Artemisinin, of plant origin, against malaria and avermectins, of bacterial origin, against intestinal, lymphatic, pulmonary or cutaneous parasites.

INRA: making significant strides

1980s-2000s:

- Hypodermosis, a parasitic bovine disease, is eradicated in France, thanks to two things: epidemiological studies and research on the biology of the parasite (fly larvae), and the recommended use of micro doses of ivermectins (0.002 mg/kg) which are100% effective at the first larval state (cf section 8).

 1990s:

- When not used properly, ivermectin is found to contaminate food: traces of the compound have been found in milk at recommended doses (0.2 mg/kg), justifying the drug’s regulated use during lactation (cf section 7).
- Adapting dosages results in a significant decrease in administered doses of ivermectin. Modifications in how the drug is administered greatly curtail the drug’s adverse effects on the environment.

2000s:

- Researchers discover that ivermectin, when applied topically to cattle, is ingested then eliminated largely in faeces, due to licking behaviour in animals. That is why it is better to apply the drug by sub-cutaneous injection (cf section 6). Science also reveals why ivermectin is toxic in hyper-sensible individuals of some dog breeds (cf section 4).  

2010s:

- Current research aims to predict and delay the onset and spread of resistance to ivermectin in parasites (cf sections 4 and 5).