Histomoniasis
The Histomoniasis even blackhead disease called, is a parasitic disease in turkeys and Gallinaceae in general. In the (predominantly older) specialist literature, there are a large number of other terms for the disease that has been caused: For example blackhead disease , histomonosis , (infectious) typhlohepatitis or enterohepatitis and typhlitis . The disease was first described in 1895 by the American parasitologist Theobald Smith on the basis of samples collected the previous year. The causative agent of histomoniasis is the flagellated parasite Histomonas meleagridis (Smith 1895: Amoeba meleagridis).
Course of the disease and symptoms
In turkeys in particular, histomoniasis leads to a severe course of the disease, with severe damage to the appendix and liver of the host.
The morbidity and mortality in infected birds is extremely high. The typical symptoms of histomoniasis are rather unspecific and infected animals show apathetic behavior, closed eyes, a stilted gait and breathing difficulties. In turkeys, the appearance of sulfur-yellow droppings as a result of liver damage is most noticeable, but in chickens it usually only results in slimy diarrhea. However, liver lesions do not occur.
However, histomoniasis can only be diagnosed with certainty after death. In turkeys, histomoniasis causes visible, necrotic lesions in the liver. In addition, the cecum of infected birds develops a severe, ulcerative inflammation, which is accompanied by a characteristic thickening of the intestinal mucosa . Young animals usually die a few days after the onset of the disease; in older animals a chronic course is often observed. The disease takes its name from the blue-red to black discoloration of the scalp, which does not always occur. Since the appearance of black combs is not a primary distinguishing feature of histomoniasis, the term black head disease is sometimes viewed as a misnomer. Sometimes other organs can also be affected by histomoniasis.
Infection and course
The parasite Histomonas meleagridis , a flagellated, pleomorphic unicellular organism, is the causative agent of histomoniasis, with a life cycle ranging from simple to complex. Histomonas meleagridis is said to be transmitted in several ways, although the meaning of the individual routes of infection is probably not fully understood. The disease can occur through ingestion of eggs or larvae of the appendix worm Heterakis gallinarum or through earthworms that act as transport hosts.
The flagellated form of Histomonas meleagridis can be found in the intestine, especially in the appendix . The lumen shape of the trophozoite has a diameter of 8 to 12 μm. In the caecum this can transform into an invasive, amoeboid form. The trophozoite accumulates on the intestinal wall of the appendix and attacks cells of the mucous membrane and submucosa , causing massive tissue damage there. Histomonas meleagridis lives and multiplies in the intestinal cells as an intracellular endoparasite. Due to the tissue damage, a fibrinogenic, ulcerative inflammation occurs in the appendix . The mucosa of the caecum thickens, and diphteroid coatings form on the lumen side. Typically, the appendix fills with a cheesy, hardening substance.
treatment
Since the histomoniasis pathogen was identified, a large number of substances have been studied over time.
Various pentavalent arsenic compounds, such as nitarsone or carbasone, were found to be effective in prophylactic use. In the European Union they are no longer approved for food-producing animals. In the USA, however, nitarson (4-nitrophenyl arsenic acid) is still used.
Nifursol , which has a preventive effect , is no longer permitted today, just like other nitrofurans; The approval of Nifursol was withdrawn across the EU on April 1, 2003.
Other active ingredients against the disease are ronidazole and dimetridazole , which are also no longer approved for chickens in the European Union.
Regular deworming of the animals has a prophylactic effect.
literature
- Michael Mielewczik, Heinz Mehlhorn, Saleh Al-Quraishy, E. Grabensteiner, M. Hess: Transmission electron microscopic studies of stages of Histomonas meleagridis from clonal cultures. In: Parasitology Research. 103, 2008, p. 745, doi : 10.1007 / s00436-008-1009-1 .
Individual evidence
- ↑ Michael Mielewczik - Diploma thesis: Light and electron microscopic examinations of chicken parasites using the example of Histomonas meleagridis , HHU Düsseldorf, 2007
- ↑ McDougald (2005) Blackhead Disease (Histomoniasis) in Poultry: A Critical Review. Avian Diseases 49 (4) pp. 462-476. 2005
- ↑ a b Lund, EE Histomoniasis. In: Diseases of poultry, 6th ed. M. Iowa State University Press, Ames, IA. pp. 990-1006. 1972.
- ↑ a b vetidata
- ↑ Bavarian State Veterinary Association, press release from June 24, 2004 ( Memento from September 27, 2007 in the Internet Archive ) (PDF; 85 kB)
- ↑ Regulation (EC) No. 1756/2002 of the Council of September 23, 2002. (PDF)
- ↑ Bayer: Black head disease in turkeys (histomonosis, typhlohepatitis enzootica)