Turkeys are the most susceptible species to histomoniasis (blackheads). Due to the losses caused by the parasitic histomonas parasite Agridis, a lot of obvious damages can be caused and the rate of these losses can reach up to 100%.

Histomoniasis causes visible lesions in the cecum and liver. For this reason, bancroscopic diagnosis is made in dead or infected turkeys. Laboratomy methods through microscopy, histology, PCR and culture can be used in definitive diagnosis.

Incidence of disease in breeders and laying hens

Histomoniasis has recently been reported as a disease of productive and laying farms. Unlike in the past, when chickens were considered asymptomatic carriers of histomonas mela agridis, today, disease is often reported in chickens with high mortality and reduced egg production.

Traditional herds may be as involved as industrial farms, and clinical signs vary from acute to rapidly increasing mortality to late death within a few weeks.

The predominant lesions reported include cecal nuclei and necrotic lesions evident in the liver. Infection with other diseases may increase mortality in chickens.

Histomoniasis has been suggested as a complementary factor in chronic E. coli infections.

Histomoniasis is often diagnosed after failure of antibiotic treatment against Escherichia coli infections. When co-infection occurs in these cases (usually after the diagnosis of Escherichia coli septicemia by necropsy and finding bacteria), antibiotic treatment is ineffective or ineffective; However, their use is based on sensitivity tests.

In these cases, histomonas mele agridis is a possible factor in subsequent deaths. Diagnosis of histomoniasis is often based on PCR examination of the cecum nuclei, which is often seen in these cases.

Due to ever-increasing regulatory constraints, no histomoniasis drugs have been registered for decades for animals consumed orally in the European market.

New veterinary premixes

The only exception is ParomomicinaHuvepharma, a veterinary premix containing active paramomycin sulfate, registered in Italy and proving that it can be used to treat histomoniasis after diagnosis in a turkey herd. It is currently the only product registered in Europe for this purpose.

Paramomycin has been shown to be an effective molecule for reducing histomoniasis losses and lesions if used in the early stages of infection. Paramomycin is an aminoglycoside antibiotic.

In addition to its antibiotic activity, paramomycin acts against several parasites. This action against the parasite causing histomoniasis has also been demonstrated and the paramycin binding site on the parasite has been shown. The need for early administration of the drug is due to the fact that paramomycin is absorbed in small amounts from the gastrointestinal tract. In the early stages of infection, the parasite is present only in the intestine (cecum) and is a place that is sensitive to drug activity. In the later stages of the infection, the parasite will move to internal organs (especially the liver) where it is difficult for the drug to reach.

Early diagnosis is critical

In order to prevent acute problems in the herd, the initial diagnosis is histomoniasis. Turkeys infected with histomoniasis will become ill, sitting silently with their eyes closed and their wings drooping (humming). Sulfur diarrhea of ​​obvious color can be seen in the herd. Dead animals should be examined necroscopically as soon as possible, and special attention should be paid to the cecum and liver.

With increasing mortality in productive and laying flocks, special attention should be paid to the cecum during necroscopy. The presence of cecal balls can indicate involvement with histomoniasis.

Another possible procedure is PCR testing to detect histomoniasis in the very early stages.

Soil is a sensitive material for finding histomonas and can help identify farms where histomonas parasites are present and are places to pay special attention to when performing necroscopy.

Paramomycin should be given as soon as the disease is present in the herd.

In addition to treatment with paramomycin, poultry management should be considered. Infected turkeys will spread the disease and must be eradicated or isolated as soon as possible.

Optimal hygiene and bed management

Optimal hygiene and litter management on the farms involved is critical to preventing the spread of the disease. Bringing a fresh and clean litter to poultry, dividing the space into several sections, removing infected birds and increasing the biosafety of the farm will reduce the spread of parasites. The importance of Heterakisgallinarum in disease transmission has always been questioned. Heterakisgallinarum can be thought of as an intermediate host for disease entry into the farm.

The flagellate form of histomonas can survive for only a few hours in the environment outside the host body, while the intracellular form of Heterakis can survive for several years.

Horizontal transmission through waterways is probably more important in the distribution of histomonas in the herd.

While chickens are better hosts for Heterakisgallinarum than turkeys, the presence of histomonas helps the worm survive and produce eggs.

It is recommended that farms on which histomonas occur be regularly dewormed to prevent infection of Heterakis eggs with histomonas (and the spread of the disease to the next or other herd) as much as possible.

This is more important in breeding and laying farms because they are better hosts for Heterakis and often live longer, allowing the disease to worsen. Therefore, deworming should be considered as an important strategy in the spread of histomoniasis.


In short, histomoniasis is a serious problem in turkeys and occurs in breeding and laying farms.

Recently, only Paromomycin (Huvepharma) has been registered in Europe (Italy) as a therapeutic agent for turkey histomoniasis. The drug needs to be prescribed in the very early stages of infection, which needs to be improved by improving the management of the infected herd. In breeders and laying hens, it is recommended that deworming be done regularly to prevent infection of Heterakis eggs with histomonas.

Translation and research: Fatemeh Davoodi

Reference: International Poultry Production, Volume 28 Number 5 (2020), Pages 27-28.

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