Histomoniasis | |
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Other names | Histomonosis, blackhead disease |
Large, pale areas in the liver of a bird infected with Histomonas meleagridis | |
Specialty | Veterinary medicine |
Histomoniasis is a commercially significant disease of poultry, particularly of chickens and turkeys, due to parasitic infection of a protozoan, Histomonas meleagridis . The protozoan is transmitted to the bird by the nematode parasite Heterakis gallinarum . [1] [2] H. meleagridis resides within the eggs of H. gallinarum, so birds ingest the parasites along with contaminated soil or food. [3] Earthworms can also act as a paratenic host.
Histomonas meleagridis specifically infects the cecum and liver. Symptoms of the infection include lethargy, reduced appetite, poor growth, increased thirst, sulphur-yellow diarrhoea and dry, ruffled feathers. The head may become cyanotic (bluish in colour), hence the common name of the disease, blackhead disease; thus the name 'blackhead' is in all possibility a misnomer for discoloration. [4] The disease carries a high mortality rate, and is particularly highly fatal in poultry, and less in other birds. Currently, no prescription drug is approved to treat this disease. [3]
Poultry (especially free-ranging) and wild birds commonly harbor a number of parasitic worms with only mild health problems from them. Turkeys are much more susceptible to getting blackhead than are chickens. Thus, chickens can be infected carriers for a long time because they are not removed or medicated by their owners, and they do not die or stop eating/defecating. H. gallinarum eggs can remain infective in soil for four years, a high risk of transmitting blackhead to turkeys remains if they graze areas with chicken feces [5] in this time frame.
Symptoms appear within 7–12 days after infection and include depression, reduced appetite, poor growth, increased thirst, sulphur-yellow diarrhoea, listlessness, drooping wings, and unkempt feathers. Young birds have a more acute disease and die within a few days after signs appear. Older birds may be sick for some time and become emaciated before death. The symptoms are highly fatal to turkeys, but effect less damage in chickens. However, outbreaks in chickens may result in high morbidity, moderate mortality, and extensive culling, leading to overall poor flock performance. [3] Concurrence of Salmonella typhmurium and E. coli was found to cause high mortality in broiler chickens. [6]
A protozoan H. meleagridis is responsible for histomoniasis of gallinaceous birds ranging from chickens, turkeys, ducks, geese, grouse, guineafowl, partridges, pheasants, and quails. The protozoan parasite is transmitted through the eggs of a nematode, Heterakis gallinarum . The eggs are highly resistant to environmental conditions, and H. meleagridis is, in turn, highly viable inside the eggs, even for years. Birds are infected once they ingest the eggs of the nematode in soil, or sometimes through earthworms which had ingested the egg-contaminated soil. Outbreak can occur rapidly from the heavily infected bird in a flock readily through normal contact between uninfected and infected birds and their droppings in the total absence of cecal worms. [7] For this reason, infection can spread very quickly. Once inside the digestive system of the host, the protozoan is moved to the cecum along with the eggs of H. gallinarum. [8]
The disease causing agent, Histomonas meliagridis, is transmitted in the eggs of the worm Heterakis gallinarum. [8] Once in the environment, the eggs are carried by earthworms. When the worms are eaten and the eggs hatch in the ceca, the pathogen is released. [9] Bird to bird transmission can also occur from cloacal drinking [10]
Visible signs of this disease are cyanosis of the head (hence, “blackhead”) and sulfur-yellow diarrhea. The pathogen causes lesions on the ceca and the liver. The ceca experience ulcerations, enlargement, and caseous masses start to form inside of them. The liver develops round, haemorrhagic, 1-2 centimeter oci that have caseous cores. [9]
Histomoniasis is characterized by blackhead in birds. H. meleagridis is released in the cecum where the eggs of the nematode undergo larval development. The parasite migrates to the mucosa and submucosa where they cause extensive and severe necrosis of the tissue. Necrosis is initiated by inflammation and gradual ulceration, causing thickening of the cecal wall. The lesions are sometimes exacerbated by other pathogens such as Escherichia coli and coccidia. Histomonads then gain entry into small veins of the blood stream from the cecal lesions and migrate to the liver, causing focal necrosis. Turkeys are noted to be most susceptible to the symptoms in terms of mortality, sometimes approaching 100% of a flock. [8] Diagnosis can be easily performed by necropsy of the fresh or preserved carcass. Unusual lesions have been observed in other organs of turkey such as the bursa of Fabricius, lungs, and kidneys. [11]
Currently, no therapeutic drugs are prescribed for the disease. Therefore, prevention is the sole mode of treatment. This disease can be prevented only by quarantining sick birds and preventing migration of birds around the house, causing them to spread the disease. [12] Deworming of birds with anthelmintics can reduce exposure to the cecal nematodes that carry the protozoan. Good management of the farm, including immediate quarantine of infected birds and sanitation, is the main useful strategy for controlling the spread of the parasitic contamination. [13] The only drug used for the control (prophylaxis) in the United States is (nitarsone) at 0.01875% of feed until 5 days before marketing. Natustat and nitarsone were shown to be effective therapeutic drugs. [14] As of the end of 2015, the FDA has proscribed arsenical drugs in poultry in the US. [15] Nifurtimox, a compound with known antiprotozoal activity, was demonstrated to be significantly effective at 300–400 ppm, and well tolerated by turkeys. [16]
The disease was initially discovered in Rhode Island in the year 1893. Soon after, it was shown to have devastating effects on the turkey industry, especially in New England, dropping production from 11 million birds in 1890 to 6.6 million in 1900. However, improvements in turkey management have curbed the effects of this disease. It has since spread across the globe. [8] It has been found in turkeys, chickens, guinea fowl, and other game birds. [9] Bobwhite quail can also be infected. [17]
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Ascaridia galli is a parasitic roundworm belonging to the phylum Nematoda. Nematodes of the genus Ascaridia are essentially intestinal parasites of birds. A. galli is the most prevalent and pathogenic species, especially in domestic fowl, Gallus domesticus. It causes ascaridiasis, a disease of poultry due to heavy worm infection, particularly in chickens and turkeys. It inhabits the small intestine, and can be occasionally seen in commercial eggs.
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Histomonas meleagridis is a species of parasitic protozoan that infects a wide range of birds including chickens, turkeys, peafowl, quail and pheasants, causing infectious enterohepatitis, or histomoniasis. H. meleagridis can infect many birds, but it is most deadly in turkeys. It inhabits the lumen of cecum and parenchyma of liver, where it causes extensive necrosis. It is transmitted by another cecal parasite, the nematode Heterakis gallinarum.
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Heterakis gallinarum is a nematode parasite that lives in the cecum of some galliform birds, particularly in ground feeders such as domestic chickens and turkeys. It causes infection that is mildly pathogenic. However, it often carries a protozoan parasite Histomonas meleagridis which causes of histomoniasis. Transmission of H. meleagridis is through the H. gallinarum egg. H. gallinarum is about 1–2 cm in length with a sharply pointed tail and a preanal sucker. The parasite is a diecious species with marked sexual dimorphism. Males are smaller and shorter, measuring around 9 mm in length, with a unique bent tail. Females are stouter and longer, measuring roughly 13 mm in length, with a straight tail end.
Heterakis is a genus of parasitic nematodes. Members of the genus are minute roundworms (pinworms), hardly 1 cm long, infecting different species of gallinaceous birds, including chickens, turkeys, ducks, geese, grouse, guineafowl, partridges, pheasants, and quail. About 10 species are placed in the genus, but classification is often ambiguous due to their close resemblance, and a number of synonyms have arisen. H. gallinarumSchrank, 1788; H. isolonchevon Linstow, 1906; and H. disparSchrank, 1870 are the best understood species in terms of prevalence, pathogenicity, and biology. They inhabit the lumen of the cecum of the host.
Trichomonas gallinae is a cosmopolitan parasite of birds including finches, pigeons, doves, turkeys, chickens, parrots, raptors. The condition in birds of prey is called frounce. It is believed to be an ancient pathogen causing frounce-like symptoms in theropod dinosaurs. The same condition in pigeons is commonly called canker.
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Infectious coryza is a serious bacterial disease of chickens, which affects respiratory system, and it is manifested by inflammation of the area below the eye, nasal discharge, and sneezing. The disease is found all over the world, causing high economic losses, which are due to stumping off and reduction of egg production in case of laying chickens. The disease was discovered early 1930s by considering clinical signs.
Airsacculitis, also known as air sacculitis, aerosacculitis, air sac disease, air sac infection, air sac syndrome and simply sac disease, is a common inflammatory condition of air sacs that occurs in birds and is caused by various microbial taxa. Having multiple different causative agents, the condition is widely distributed around the world.