Effect of temperature on the development of infective small strongyle

On small farms and in small pastures and paddocks, one of the most effective ways to control intestinal parasites in horses is the removal of feces before infective larvae form. But how often? It has been long known that warm humid conditions help the parasites prosper, and cold dry conditions slow down their development. Here this is demonstrated along with numbers attached to specific conditions. When cold, infective larvae development could be as long as 22 days. When hot as short as 4 days. These numbers could form the basis for the timing of fecal removal from horse premises.
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Effect of temperature on the development of the free-living stages of horse cyathostomins
Vet Parasitol Reg Stud Reports. 2022 Feb;28:100687.
Authors
A Merlin 1 , N Ravinet 2 , C Sévin 3 , M Bernez-Romand 3 , S Petry 3 , M Delerue 4 , L Briot 4 , A Chauvin 2 , J Tapprest 3 , L Hébert 3
Affiliations

1 ANSES, Laboratory for Animal Health, Normandy site, Physiopathology and Epidemiology of Equine Diseases Unit, 14430 Goustranville, France. Electronic address: aurelie.merlin@anses.fr.
2 INRAE, Oniris, BIOEPAR, 44300 Nantes, France.
3 ANSES, Laboratory for Animal Health, Normandy site, Physiopathology and Epidemiology of Equine Diseases Unit, 14430 Goustranville, France.
4 French horse and riding institute (IFCE), 61310 Gouffern-en-Auge, France.

PMID: 35115120
DOI: 10.1016/j.vprsr.2022.100687

Abstract

Cyathostomins (small strongyles) are considered as the most prevalent and pathogenic parasites of grazing horses. The development on pastures of the free-living stages of these gastrointestinal worms is particularly influenced by outdoor temperature. Understanding the bionomics of free-living stages is an important prerequisite to implement mathematical models designed to assess the parasitic risk for grazing equids. The aim of this study was to assess the effect of 3 constant temperatures under laboratory conditions (10 ± 1 °C, 23 ± 2 °C, 30 ± 2 °C) (50 degrees, 73 degrees, 86 degrees Fahrenheit) and one fluctuating temperature under outdoor conditions (mean: 17 ± 4 °C) on the minimum time taken by cyathostomin eggs to develop into first/second stage larvae (L1/L2) then into infective third-stage larvae (L3) in horse faeces. According to the temperatures, the minimum time taken by eggs to develop into L1/L2 was between 1 and 3 days and into L3 between 4 and 22 days. At 10 °C, the development time of eggs into L3 was the longest and at 30 °C the fastest. The results were consistent with historically available data and their compilation should lead to the improvement of parameterised models assessing the parasitic risk period in grazing equids.