PCR detection of Heterakis gallinarum in environmental samples

Concurrent Histomonas meleagridis and Hemorrhagic Enteritis Virus Infection in a Turkey Flock with Recurrent History of Blackhead Disease

Intestinal health is one of the key factors required for the growth and production of turkeys. Histomoniasis (blackhead disease), caused by a protozoan parasite, Histomonas meleagridis, is a reemerging threat to the turkey industry. Increased incidences of histomoniasis have been reported in recent years due to withdrawal of antihistomonas treatments. H. meleagridis affects ceca and causes cecal inflammation and necrosis. H. meleagridis migrates from ceca to the liver and causes liver necrosis, resulting in high mortalities. Ironically, field outbreaks of histomoniasis are not always associated with high mortalities, while low mortalities have also been documented. There are several exacerbating factors associated with high mortality rates in histomoniasis outbreaks, with concurrent infection being one of them. Recurrent histomoniasis outbreaks in a newly constructed barn were documented, and concurrent infection of H. meleagridis and hemorrhagic enteritis virus was confirmed. Currently, neither commercial vaccines nor prophylactic or therapeutic solutions are available to combat histomoniasis. However, there are treatments, vaccines, and solutions to minimize or prevent concurrent infections in turkeys. In addition to implementing biosecurity measures, measures to prevent concurrent infections are critical steps that the turkey industry can follow to reduce mortality rates and minimize the production and economic losses associated with histomoniasis outbreaks.

Mapping the poultry insectome in and around broiler breeder pullet farms identifies new potential Dipteran vectors of Histomonas meleagridis

BACKGROUND

Histomonas meleagridis can infect chickens and turkeys. It uses the eggs of the cecal worm Heterakis gallinarum as a vector and reservoir. Litter beetles (Alphitobius diaperinus) and other arthropod species have been implicated as potential vectors, but little information about other arthropod species as potential vectors is known.

METHODS

Four broiler breeder pullet farms were sampled every 4 months. On each farm, three types of traps were set inside and outside two houses. Trapped arthropod specimens were morphologically identified at order level and grouped into families/types when possible. Selected specimens from abundant types found both inside and outside barns were screened for H. meleagridis and H. gallinarum by qPCR.

RESULTS

A total of 4743 arthropod specimens were trapped. The three most frequently encountered orders were Diptera (38%), Coleoptera (17%), and Hymenoptera (7%). Three hundred seventeen discrete types were differentiated. More arthropods were trapped outside than inside. Alpha diversity was greater outside than inside but not significantly influenced by season. The composition of the arthropod populations, including the insectome, varied significantly between trap location and seasons. Up to 50% of litter beetles tested positive for H. meleagridis DNA 4 months after an observed histomonosis outbreak. Sporadically litter beetles were positive for H. gallinarum DNA. Thirteen further arthropod types were tested, and specimens of four Dipteran families tested positive for either one or both parasites.

CONCLUSIONS

This study describes the insectome in and around broiler breeder pullet farms and identifies new potential vectors of H. meleagridis through qPCR. The results show a limited but present potential of arthropods, especially flies, to transmit histomonosis between farms.

Histomonosis in Poultry: A Comprehensive Review

Histomonas meleagridis, the etiological agent of histomonosis, is a poultry parasite primarily detrimental to turkeys. Characteristic lesions occur in the liver and ceca, with mortalities in turkey flocks often reaching 80-100%. Chickens and other gallinaceous birds can be susceptible but the disease was primarily considered sub-clinical until recent years. Treating and preventing H. meleagridis infection have become more difficult since 2015, when nitarsone was voluntarily removed from the market, leaving the poultry industry with no approved prophylactics, therapeutics, or vaccines to combat histomonosis. Phytogenic compounds evaluated for chemoprophylaxis of histomonosis have varied results with in vitro and in vivo experiments. Some recent research successes are encouraging for the pursuit of antihistomonal compounds derived from plants. Turkeys and chickens exhibit a level of resistance to re-infection when recovered from H. meleagridis infection, but no commercial vaccines are yet available, despite experimental successes. Safety and stability of live-attenuated isolates have been demonstrated; furthermore, highly efficacious protection has been conferred in experimental settings with administration of these isolates without harming performance. Taken together, these research advancements are encouraging for vaccine development, but further investigation is necessary to evaluate proper administration age, dose, and route. A summary of the published research is provided in this review.

Heterakis gallinarum and Histomonas meleagridis DNA persists in chicken houses years after depopulation

The poultry pathogen Histomonas meleagridis is transmitted by chicken cecal worms (Heterakis gallinarum) and is potentially transmitted by second order insect vectors and paratenic hosts. Darkling beetles (Alphitobius diaperinus) are poultry farm pests that infest barns. An outstanding question is the degree to which darkling beetles transmit both Heterakis and Histomonas. In this study we monitored populations of darkling beetles and assessed their positivity for both Heterakis and Histomonas by PCR. Uniquely, this study was conducted during the scheduled deconstruction of Auburn University's Poultry Research Farm. Therefore, we were able to monitor beetle and litter infection status months and years after bird depopulation. The duration of our monitoring continued through three seasons. We show that environmental DNA from both Heterakis and Histomonas persist in the environment long after prior infections, even in the absence of living Heterakis and its hosts. Finally, in an intensive search for live Heterakis, we discovered reniform nematodes (plant parasitic nematodes) residing in the soil floor of poultry farms.

Two Blackhead Disease Outbreaks in Commercial Turkey Flocks Were Potentially Exacerbated by Poor Poult Quality and Coccidiosis

Field visits at two different farms suggest a correlation between commercial turkey (Meleagridis gallopavo) flocks having increased mortality from blackhead disease (histomoniasis) if they suffer from poor poult quality at placement and coccidiosis (Eimeria spp.) before age 6 wk. In both cases, the flocks were all-in/all-out with curtain-sided houses and received a coccidiosis vaccine on day of hatch. At Farm I 2018, poults from different hatcheries were placed in two houses on the same farm (Houses 1 and 2). House 2 had poults considered poor quality and suffered from mortality associated with coccidiosis at 2 and 4 wk of age. At 8 wk, blackhead disease was diagnosed in both houses by postmortem examination. House 2 had mortality of >2000 poults, and the subpopulation of necropsied poults had gross lesions characteristic of histomoniasis. Gross lesions associated with blackhead disease were only found in eight poults in House 1, which was populated with good-quality poults and did not have a second spike in mortality due to coccidiosis. The Farm II 2020 poults were delivered from the same hatchery onto a three-house farm (Houses A, B, and C). House C had poults that were considered poor quality and had mortality associated with coccidiosis at 3 wk of age. At 8-9 wk, House C had mortality approaching 1000 birds, with all poults examined postmortem having clinical signs of blackhead disease. Houses A and B were populated with good-quality poults and had no diagnosed mortality from coccidiosis or blackhead disease. The similarity of these two cases suggest that poult quality at placement coupled with coccidiosis before 6 wk of age can influence the severity of blackhead disease in commercial turkey flocks.

Preliminary data on Ascaridia galli infections in Gallus gallus domesticus and the development of a specific primer based on the NADH dehydrogenase subunit 4

One major problem of chicken (Gallus gallus domesticus) farming was various parasitic infections, especially Ascaridia galli that can cause the Ascaridiosis and is commonly found worldwide. The purpose of this study was to investigate the epidemiological situation of gastrointestinal tract parasitic infections and to develop species-specific primer for A. galli detection. A total of 247 chicken gastrointestinal tract specimens from 5 fresh markets in Bangkok. The species-specific primers of A. galli were manually designed using the mitochondrial genome at the NADH dehydrogenase subunit 4 (MT-ND 4) gene. As a result, PCR assays were optimized for the specific PCR product approximately 198 bp with the optimal temperature of 51 °C. In addition, sensitivity tests provided the detection of adult and egg stages at the minimum concentrations of 156.3 ng and 2.8 ng (70 eggs), respectively. This research can be used as preliminary information regarding the epidemic situation of gastrointestinal tract infections in chickens and detection of A. galli infection in definitive hosts, which plans programs for the effective control and prevention of parasitic infections.

Heterakis gallinarum, the Cecal Nematode of Gallinaceous Birds: A Critical Review

Heterakis gallinarum is a heavily prevalent poultry parasite that thrives in the ceca of various species of gallinaceous birds. It is a small roundworm, measuring between 4 and 15 mm long, in the family Heterakidae. Heterakis gallinarum has a direct life cycle not requiring an intermediate host to complete development, and it is generally believed that poultry raised at high density on litter are at greatest risk for accumulating large numbers of the nematode. This species typically only causes mild pathology that does not significantly affect bird performance. However, H. gallinarum is recognized as an economically important parasite by the poultry industry because its ovum serves as the vector for the protozoal parasite Histomonas meleagridis, the cause of histomonosis in poultry. Diagnosis of the nematode typically relies on fecal egg counts, which are prone to false negative diagnoses. Molecular tools are available for studying the nematode and diagnosing infected flocks. Treating and preventing H. gallinarum infection is made difficult due to the low efficacy of anthelmintics for eradicating H. gallinarum from infected birds and of disinfectants for destroying H. gallinarum ova on contaminated farms.