Critical Review: Future Control of Blackhead Disease (Histomoniasis) in Poultry

Clark, Steven; Kimminau, E.A.

doi:10.1637/11593-012517-reviewr

Cited by 30 publications

(26 citation statements)

References 78 publications

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“…Vaccines being evaluated for use in control of histomoniasis would be highly beneficial for backyard flock owners as well as commercial flocks. 5,25,34 Most fungal infections are opportunistic and can be attributed to poor management of the flock environment. Evidence of fungal infection in flocks may signify issues with environmental and equipment sanitation and moldy feed and litter.…”

Section: Discussionmentioning

confidence: 99%

Causes of mortality in backyard poultry in eight states in the United States

et al. 2019

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A comprehensive understanding of common diseases of backyard poultry flocks is important to providing poultry health information to flock owners, veterinarians, and animal health officials. We collected autopsy reports over a 3-y period (2015-2017) from diagnostic laboratories in 8 states in the United States; 2,509 reports were collected, involving autopsies of 2,687 birds. The primary cause of mortality was categorized as infectious, noninfectious, neoplasia or lymphoproliferative disease, or undetermined. Neoplasia or lymphoproliferative disease was the most common primary diagnosis and involved 42% of the total birds autopsied; 63% of these cases were diagnosed as Marek's disease or leukosis/sarcoma. Bacterial, parasitic, and viral organisms were commonly detected, involving 42%, 28%, and 7% of the birds autopsied, respectively, with 2 or more organisms detected in 69% of birds. Our findings demonstrate the importance of educating flock owners about disease prevention and biosecurity practices. The detection of zoonotic bacteria including paratyphoid salmonellae, Campylobacter spp., Listeria monocytogenes, and Mycobacterium avium, and the detection of lead and other heavy metals, indicate public health risks to flock owners and consumers of backyard flock egg and meat products.

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Section: Discussionmentioning

confidence: 99%

Causes of mortality in backyard poultry in eight states in the United States

et al. 2019

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“…Due to the imposed ban on effective medication used for prevention or treatment of histomonosis in the EU and the USA [2], an increased number of histomonosis outbreaks have been noticed with varying mortalities, affecting turkey flocks of different size, age and sex, well documented from outbreaks in France [3]. For 2016, 101 outbreaks were reported in the USA which was nearly doubled to those of the preceding year [14].…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2019

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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.

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“…Recently, this view has shifted as studies show that both chickens and turkeys demonstrate clinical signs such as apathy, depression, and ruffled feathers, together with decreased feed and water uptake (Liebhart, et al, 2017). Histomonas meleagridis has now been shown to impact chickens in multiple different production systems, including reduced feed conversion in broilers, and decreased egg quality and production in layers and breeders, both caged and cage-free (Clark and Kimminau, 2017;Grafl, et al, 2011;Liebhart, et al, 2013) Despite these significant effects on health and production, there are currently no FDA approved treatments for histomoniasis, making control of this diseases dependent on control of the H. gallinarum vector.…”

Section: Introductionmentioning

confidence: 99%

Fenbendazole resistance in Heterakis gallinarum, the vector of Histomonas meleagridis, the causative agent of Blackhead Disease in poultry

Collins

Jordan

A³

et al. 2021

Preprint

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Due to their ubiquity, management of parasites is a common and important factor for profitable production of poultry. Heterakis gallinarum, the cecal nematode, is the most common nematode parasite of poultry. While typically causing no pathology on its own, H. gallinarum is the vector of Histomonas meleagridis, a protozoan parasite that causes blackhead disease. Histomonas meleagridis is highly pathogenic in turkeys, potentially causing high mortality. In contrast, disease caused by H. meleagridis is much less severe in chickens, where it primarily reduces productivity without manifestations of clinical disease. There are no approved treatments for H. meleagridis, making control reliant on control of the helminth vector through the use of fenbendazole (FBZ) the only drug labeled for treatment of H. gallinarum in the United States We were contacted by an industry veterinarian regarding health-related concerns in a breeder-broiler house due to histomoniasis, despite frequent anthelmintic treatments. Since we had recently diagnosed resistance to FBZ in Ascaridia dissimilis, a closely related nematode of turkeys, we were interested to determine if H. gallinarum had also evolved resistance to FBZ. Heterakis gallinarum eggs were isolated from litter collected from the house and used to infect 108 chickens. Treatment groups included a non-treated control, a label-dose and a 2X-label dose of FBZ, with 36 birds per group divided into two replicate pens of 18 birds each. Birds were placed at 1-day post hatch, and at 3 weeks of age were infected with 150 embryonated eggs via oral gavage. Two weeks post infection, treated birds were administered a minimum of either a label- or 2X label-dose of FBZ in water for 5 days (SafeGuard® Aquasol, 1mg/kg BW). To ensure that all birds consumed the full intended dose at a minimum, the dosage was calculated using 1.25 times the average body weight. One-week post treatment, birds were euthanized, ceca removed, and parasites enumerated. Efficacy was calculated by comparing the total numbers of worms recovered from each treatment group to the numbers recovered in the non-treated control group. There were no significant differences in worm numbers recovered from any of the three groups (p-value=0.81). There also was no efficacy benefit to treatment with a 2X dose; H. gallinarum worm counts were reduced by 42.7% and 41.4%, for the label and 2X dosages, respectively. These data provide strong evidence that H. gallinarum has developed resistance to FBZ. Consequently, in houses infected with FBZ-resistant H. gallinarum, H. meleagridis will be able to cycle through the birds in an unrestricted manner. Further investigation is needed to determine the prevalence of resistance in H. gallinarum on chicken farms, but it is clear this has the potential to have a large-scale economic impact on the poultry industry. These data when viewed together with our recent findings of FBZ resistance in A. dissimilis, suggest that drug resistance in ascarid nematodes may be an important emerging problem on poultry operations.

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Critical Review: Future Control of Blackhead Disease (Histomoniasis) in Poultry

Cited by 30 publications

References 78 publications

Causes of mortality in backyard poultry in eight states in the United States

Causes of mortality in backyard poultry in eight states in the United States

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

Fenbendazole resistance in Heterakis gallinarum, the vector of Histomonas meleagridis, the causative agent of Blackhead Disease in poultry

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