Blackhead disease

The blackhead or Histomoniasis is an infectious disease of turkeys and gallinaceous birds in general. In the ( mostly older ) literature there is a variety of other alternative names for the induced disease: for example, Blackhead disease, Histomoniasis, (infectious ) typhlohepatitis or Enterohepatitis and typhlitis. The first description of the disease was performed in 1895 by the parasitologists Theobald Smith on samples that were collected in the previous year. Causative agent of blackhead disease is the flagellated parasite Histomonas meleagridis (Smith 1895: Amoeba meleagridis ).

The Clinic for poultry, pet birds, reptiles and fish of the University of Veterinary Medicine Vienna has begun to an appropriate research project.

Disease course and symptoms

Especially with the turkeys Histomoniasis leads to a severe course, with the caecum and liver of the host are severely damaged. The morbidity and mortality in infected birds is extremely high. The typical symptoms of Histomoniasis are rather non-specific and infected animals show an apathetic behavior, closed eyes, a stilted gait and difficulty in breathing. In turkeys, the occurrence of sulfur- yellow feces as a result of liver damage is most noticeable in chickens occurs but usually only to a slimy diarrhea. Lesions of the liver, however, do not occur. However, can be safely diagnosed Histomoniasis only postmortem. In turkeys the Histomoniasis cause visible necrotic lesions in the liver. In addition, it takes in the cecum of infected birds to severe ulcerative inflammation which is associated with a characteristic thickening of the mucosa. Young animals usually die a few days after the outbreak of the disease in the elderly is often a chronic course observed. The name has the disease of a blue- red to black discoloration of the scalp, but these do not always occur. Since the occurrence of black combing but is not a primary distinguishing feature of the histomoniasis, the term blackhead disease is sometimes referred to as a Misnomer. Sometimes, other organs may be affected by the Histomoniasis.

Infection and progression

The parasite Histomonas meleagridis, a flagellated, unicellular pleomorphic, is the causative agent of the so-called black head, with the life cycle proves to be simple to complex. The transmission of Histomonas meleagridis to be made in several ways, with the full meaning of the individual routes of infection but is probably not fully understood. The disease can occur through the intake of eggs or larvae of the cecal worm Heterakis gallinarum or by earthworms, which act as transport hosts.

In the intestine, especially in the cecum, the flagellate Histomonas meleagridis form of find. The lumen shape of the trophozoites has a diameter of 8 to 12 microns. In the cecum can convert them into an invasive, amoeboid shape. Anneals to the trophozoite to the intestinal wall of the caecum and attack the cells of the mucosa and submucosa, wherein it causes massive tissue damage there. In the intestinal cells survived and Histomonas meleagridis replicates as an intracellular endoparasite. On the basis of tissue damage occurs in the cecum to a fibrogenic, ulcerative inflammation. The mucosa of the caecum thickens, are formed on the lumen side diphtheroids coverings. Typically, the cecum filled with a cheesy, hardening substance.

Treatment

Since the identification of the pathogen of Histomoniasis was more or less continuously locate therapeutic and prophylactic agents for the control of blackhead disease. A plurality of substances was investigated in the course of this time.

Various pentavalent arsenic compounds, such as Nitarson or Carbason proved to be effective in the prophylactic use. In the European Union they are no longer approved for food-producing animals. In the U.S., however Nitarson (4- Nitrophenylarsensäure ) is still used.

Also, the preventive action nifursol is today, as well as other nitrofurans, no longer permitted; the approval of nifursol was EU-wide revoked on 1 April 2003.

Other drugs against the disease are ronidazole and dimetridazole which are not approved in the European Union for chickens birds also.

Prophylactic effect a regular deworming of animals.