PCR and serology confirm the infection of turkey hens and their resilience to histomonosis in mixed flocks following high mortalities in toms

Abstract

Background Histomonosis, caused by the protozoan parasite Histomonas meleagridis , is a severe disease especially in turkeys where it can cause high mortalities. Recently, outbreaks were described in which turkey hens showed no clinical signs despite high mortalities in toms, from which they were separated only by a wire fence. The present study investigated three similar outbreaks of histomonosis whereby in two of them only a few hens were being affected and none in the third. Hens from all flocks were kept until end of production and slaughtered as scheduled. However, in all three cases, the disease progressed in toms reaching nearly 100% within two weeks. Methods Following diagnosis of the disease, tissue samples were obtained from toms and hens at necropsy. Environmental dust, cloacal swabs and blood were taken on three successive farm visits within compartments of hens and toms and tested by real-time PCR or ELISA. The DNA from a total of 18 samples positive for H. meleagridis was further subjected to conventional PCR utilizing the 18S rRNA primers and sequenced for phylogenetic analysis. Results All tissue samples and some cloacal swabs were tested positive. Dust samples confirmed the presence of H. meleagridis DNA that spread within entire houses up to 6 weeks after the first clinical signs of histomonosis. Sequence analysis of the 18S rRNA locus demonstrated the presence of the same strain in birds of both sexes within each of the turkey houses. Investigation of serum samples two weeks post-initial diagnosis and prior to euthanasia resulted in antibody detection in 73% of toms and 70% of hens. Until the end of the investigation the number of positive hens per farm increased up to 100% with mean OD-values approaching those noticed in toms prior to euthanasia. Conclusions For the first time it could be demonstrated that turkey hens kept in the same house as toms became infected during fatal outbreaks in toms. This highlights the value of different diagnostics methods in order to trace the parasite in connection with the host response. The strange phenomenon that only single hens succumb to the diseases despite being infected requires further investigations.

Feed Composition and Isolate of Histomonas meleagridis Alter Horizontal Transmission of Histomonosis in Turkeys. Proof of Concept

“…The authors hypothesized that the gut microbiota and a variation in the immune response between males and females could be responsible for the difference in the disease outcome (15). Unfortunately, the stocking density was not reported in the two compartments of the house, nor the composition of the diets nor if the diets were different among males and females (15). It is still not clear if histomonosis can be transmitted by contacting fresh feces in the litter or only by direct cloacal contact between turkeys and which factors would affect the survival of histomonads in the litter.…”

“…Variability in the incidence and outcome of histomonosis in outbreaks in turkey farms is also commonly reported, with only one house within a farm with multiple houses being affected; only one sex in mixed flocks, or only one section within a house ( 14 , 15 ). Sulejmanović and colleagues ( 15 ) reported three outbreaks of histomonosis in turkey houses where toms and hens were raised together but in different compartments separated by a wire mesh. In the three outbreaks, only toms were severely affected by histomonosis.…”

“…The presence of histomonads was also confirmed in high numbers in dust samples by PCR. The authors hypothesized that the gut microbiota and a variation in the immune response between males and females could be responsible for the difference in the disease outcome ( 15 ). Unfortunately, the stocking density was not reported in the two compartments of the house, nor the composition of the diets nor if the diets were different among males and females ( 15 ).…”

Protozoal infections of young turkeys in the conditions of industrial farms

“…Currently, in the conditions of the development of the industry on an industrial basis, when a large number of birds are kept in a limited area, there is a high risk of eimeriosis, cryptosporidiosis, histomonosis and other parasitic diseases [1,2,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

“…Microgametes (16) and macrogametes (16a) are formed from micro-and macrogamonts. The formed microgametes (17) and macrogametes (17a) destroy intestinal epithelial cells and exit in large numbers into the intestinal lumen, where microgametes and macrogametes (18) merge to form a zygote (19). The zygote is covered with a protective shell and becomes an oocyst, which is excreted into the external environment with droppings (20).…”