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Infectivity of Histomonas meleagridis in ducks
M P Callait-Cardinal1, C Chauve, M C Reynaud
1Laboratoire de Parasitologie, U.M.R. INRA/ENVL 958, 69280, Marcy-l'Etoile, France. mp.callait@vet-lyon.fr
Abstract:
The susceptibility of mule and muscovy ducks to "blackhead" disease caused by Histomonas meleagridis was studied, using an experimental intracloacal inoculation. Turkeys were used as controls. Morbidity, mortality and body weight gain were recorded regularly during the experiments. A direct examination of the caecal content was made to determine the absence or presence of the parasite. Gross and microscopic lesions were observed on days 7, 14, 21, 28 and 35 post infection to evaluate any clinical histomoniosis in ducks and to appraise the histomonad's carriage. A scoring system was developed both for gross and histological lesions of the caecum and liver. Infected mule and muscovy ducks (n = 83) never developed any clinical signs of histomoniasis. Weight gains of infected mule and muscovy ducks were similar to those of uninfected ducks. In 67% of the ducks (56/83), it was possible to demonstrate the parasite in the caecal content throughout the experiment. Typical macroscopic caecal lesions were observed in five of the ducks between days 7 and 21 post infection, with a caecal necropsy main lesion score (MLS = 1.6) less severe than that in turkeys (MLS = 2.9). Only caecal histological lesions occurred in six of the cases. Therefore, ducks do not seem to be a susceptible host for "blackhead" but may act as carrier animals for H. meleagridis. The virulence was apparently not changed, since 67% of turkeys (10/15) infected with the caecal content of positive ducks displayed classical signs of blackhead disease. Even if H. meleagridis alone does not represent a substantial danger in the duck production, its infectivity should to be taken into account in the transmission to more susceptible species.
Insights
Mule and Muscovy ducks are not susceptible to blackhead disease caused by Histomonas meleagridis but can carry and transmit the parasite to turkeys. Ducks showed no clinical signs but shed the parasite, infecting 67% of control turkeys.
Area of Science:
- Veterinary Parasitology
- Avian Pathology
- Infectious Diseases
Background:
- Blackhead disease, caused by Histomonas meleagridis, primarily affects turkeys and other gallinaceous birds.
- Understanding host susceptibility and carrier states is crucial for disease control in poultry farming.
Purpose of the Study:
- To investigate the susceptibility of mule and Muscovy ducks to Histomonas meleagridis.
- To determine if ducks can act as carriers of the blackhead disease parasite.
Main Methods:
- Experimental intracloacal inoculation of ducks with Histomonas meleagridis.
- Turkeys were used as controls.
- Monitoring morbidity, mortality, weight gain, and performing direct parasite examination, gross, and microscopic lesion scoring.
Main Results:
- Infected ducks (n=83) showed no clinical signs of histomoniasis and similar weight gains to uninfected ducks.
- Histomonas meleagridis was detected in the caecal content of 67% of infected ducks.
- Mild caecal lesions were observed in some ducks, but were less severe than in turkeys; ducks are not susceptible hosts but potential carriers.
Conclusions:
- Ducks are not a susceptible host for blackhead disease but can act as carriers of Histomonas meleagridis.
- The parasite's virulence remained unchanged, as duck-derived material infected 67% of turkeys.
- While H. meleagridis poses little direct risk to ducks, its role in transmission to susceptible species must be considered.
