Susceptibility of wild turkeys (Meleagris gallopavo) to experimental West Nile virus infection.

Since the introduction of West Nile virus (WNV) to North America in 1999, WNV is estimated to have contributed to population-level declines in numerous avian species. However, the potential impacts of this virus on many free-ranging upland game bird species, including the wild turkey (Meleagris gallopavo), which is undergoing regional population declines, remain unknown. Herein, two age groups (∼5 to 6 weeks and ∼15 to 16 weeks post-hatch) of juvenile wild turkeys were subcutaneously inoculated with WNV, sampled daily from 1 to 7 days post-inoculation (dpi), and euthanized on 14 dpi. No clinical signs and minimal gross lesions were attributable to WNV infection. Peak viraemia titres were similar between age groups (<101.7 to 104.6 plaque-forming units [PFU]/ml), but the duration of viraemia was longer in the old group (3-4 days) than in the young group (0-3 days). Intermittent oral and/or cloacal viral shedding from 2 to 7 dpi was detected in both age groups. No infectious virus was detected in the heart, brain, kidney, skeletal muscle, spleen, and feathers from WNV-inoculated turkeys euthanized on 14 dpi. All WNV-inoculated birds seroconverted by 14 dpi, as well as two co-housed sham-inoculated birds. The most consistent microscopic lesions among all WNV-inoculated birds were mild lymphoplasmacytic myocarditis and encephalitis. Minimal immunohistochemical labelling was detected in tissues in addition to scant macrophages within the blood, spleen, and bone marrow. These data suggest WNV is unlikely to pose a significant risk to wild turkey populations, although the possibility remains that WNV may indirectly decrease fitness or predispose wild turkeys to other health stressors.RESEARCH HIGHLIGHTS Clinical disease was not observed in wild turkeys experimentally infected with WNV.Pathology attributed to WNV was mild and included brain and heart inflammation.Viraemias suggest WNV-infected wild turkeys do not play a role in WNV transmission.No age-associated differences in WNV clinical disease or pathology were observed.

Surveillance for Borrelia spp. in Upland Game Birds in Pennsylvania, USA.

The Borrelia genus contains two major clades, the Lyme borreliosis group, which includes the causative agents of Lyme disease/borreliosis (B. burgdorferi sensu stricto and other related B. burgdorferi sensu lato genospecies), and the relapsing fever borreliosis group (B. hermsii, B. turicatae, and B. parkeri). Other unclassified reptile- and echidna-associated Borrelia spp. (i.e., B. turcica and 'Candidatus Borrelia tachyglossi', respectively) do not belong in either of these two groups. In North America, Borrelia spp. from both of the major clades are important pathogens of veterinary and public health concern. Lyme disease is of particular interest because the incidence in the northeastern United States continues to increase in both dogs and humans. Birds have a potentially important role in the ecology of Borrelia species because they are hosts for numerous tick vectors and competent hosts for various Borrelia spp. Our goal was to investigate the prevalence of Borrelia spp. in four free-living species of upland game birds in Pennsylvania, USA including wild turkey (Meleagris gallopavo), ruffed grouse (Bonasa umbellus), ring-necked pheasants (Phasianus colchicus), and American woodcock (Scolopax minor). We tested 205 tissue samples (bone marrow and/or spleen samples) from 169 individuals for Borrelia using a flagellin gene (flab) nested PCR, which amplifies all Borrelia species. We detected Borrelia DNA in 12% (24/205) of samples, the highest prevalence was in wild turkeys (16%; 5/31), followed by ruffed grouse (13%; 16/126) and American woodcock (3%; 1/35). All pheasants (n = 13) were negative. We sequenced amplicons from all positive game birds and all were B. burgdorferi sensu stricto. Our results support previous work indicating that certain species of upland game birds are commonly infected with Borrelia species, but unlike previous studies, we did not find any relapsing fever borreliae.

Surveillance for Heterakis spp. in Game Birds and Cage-Free, Floor-Raised Poultry in Pennsylvania.

Histomoniasis is a significant disease of gallinaceous birds caused by Histomonas meleagridis. Transmission of this parasite is dependent on use of the cecal nematode Heterakis gallinarum. To define the host range of this nematode, cecal contents from 399 game birds and poultry, representing eight species, were examined for Heterakis spp. The majority of these species (five of eight) were infected with Heterakis nematodes. Heterakis gallinarum was detected in free-ranging wild turkeys (Meleagridis gallopovo), captive-raised ring-necked pheasants (Phasianus colchicus), chukars (Alectoris chukar), and domestic chickens (Gallus gallus domesticus), whereas H. isolonche was found in ruffed grouse (Bonasa umbellus). No Heterakis species were identified in the domestic turkey (Meleagridis gallopovo), American woodcock (Scolopax minor), and dabbling duck (Anas spp.) samples. Genetic characterization indicated that nematodes identified as H. gallinarum were present in two distinct clades. One clade of H. gallinarum sequenced from this study grouped with chicken-derived sequences from other countries. The other group of sequences consisted of a sister clade to a group of parasites morphologically identified as H. isolonche. Currently it is unknown if this group represents a genetic variant of H. gallinarum, a variant of H. isolonche, or a novel species. These results indicate Heterakis infection varies among poultry and game bird species but is common among select gallinaceous species in Pennsylvania.

Nota de investigación- Vigilancia de Heterakis spp. en aves de caza y aves comerciales criadas en piso sin jaulas en Pennsylvania. La histomoniasis es una enfermedad importante de las aves gallináceas causada por Histomonas meleagridis. La transmisión de este parásito depende de la interacción con el nematodo cecal Heterakis gallinarum. Para definir el rango de hospedadores de este nematodo, se examinaron los contenidos cecales de 399 aves de caza y aves domésticas, que representaron a ocho especies, para detectar Heterakis spp. La mayoría de estas especies (cinco de ocho) estaban infectadas con nematodos Heterakis. Heterakis gallinarum se detectó en pavos silvestres (Meleagridis gallopavo), faisanes comunes criados en cautiverio (Phasianus colchicus), perdiz chukar (Alectoris chukar) y pollos domésticos (Gallus gallus domesticus), mientras que H. isolonche se encontró en el grévol engolado (Bonasa umbellus). No se identificaron especies de Heterakis en las muestras de pavo doméstico (Meleagridis gallopavo), chocha americana (Scolopax minor) y pato chapuceadores (Anas spp.). La caracterización genética indicó que los nematodos identificados como H. gallinarum estaban presentes en dos clados distintos. Un clado de H. gallinarum secuenciado de este estudio agrupado con secuencias derivadas de pollos de otros países. El otro grupo de secuencias consistió en un clado hermano de un grupo de parásitos identificados morfológicamente como H. isolonche. Actualmente se desconoce si este grupo representa una variante genética de H. gallinarum, una variante de H. isolonche o una especie nueva. Estos resultados indican que la infección por Heterakis varía entre las aves domésticas y las especies de aves de caza, pero es común entre las especies de gallináceas seleccionadas en Pennsylvania.

Isolation and Genetic Characterization of Toxoplasma gondii from Tissues of Wild Turkeys (Meleagris gallopavo) in Pennsylvania.

Toxoplasmosis in wild turkeys (Meleagris gallopavo) is of epidemiological interest because turkeys feed from the ground, and detection of infection in turkeys indicates contamination by oocysts in the environment. During the 2018 spring hunting season in Pennsylvania, fresh (unfixed, not frozen) samples were obtained from 20 harvested wild turkeys and tested for Toxoplasma gondii infection. Hearts from all wild turkeys and skeletal muscle from 1 were bioassayed for T. gondii by inoculation in outbred Swiss Webster (SW) and interferon-gamma gene knockout (KO) mice. Antibodies to T. gondii were detected in 1:5 dilution of neat serum from 5 of 15 wild turkeys and in fluid from the heart of 1 of 4 wild turkeys with the modified agglutination test (MAT); neat serum was not available from 4 wild turkeys. Viable T. gondii was isolated from hearts of 5 wild turkeys, 1 with MAT of 1:10, 1 with MAT of 1:5, and 3 seronegative (MAT < 1:5). Toxoplasma gondii was isolated from both heart and skeletal muscle in the 1 wild turkey that had skeletal muscle submitted. The KO mice inoculated with tissue from all 5 infected wild turkeys died or were euthanatized when ill, 7-21 days post-inoculation (PI). Tachyzoites were detected in lungs of all KO mice, and the T. gondii strains were successfully propagated in cell culture. The SW mice inoculated with tissues of wild turkeys remained asymptomatic, and tissue cysts were seen in the brains of infected mice when euthanatized in good health at 46 days PI; 1 of the 2 SW mice inoculated with the heart of 1 turkey died on day 26, and tachyzoites were detected in its lung. Genetic typing on DNA extracted from culture-derived tachyzoites using the PCR restriction fragment length polymorphism with 10 genetic markers (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) revealed that 4 isolates belonged to ToxoDB PCR-RFLP genotype #5 and 1 was genotype #216.

Evaluation of Cytology for Diagnosing Avian Pox in Wild Turkeys ( Meleagris gallopavo).

Avian pox virus is a common cause of proliferative skin disease in wild turkeys ( Meleagris gallopavo); however, other etiologies may produce grossly indistinguishable lesions. Common methods for diagnosing avian pox include histopathology, virus isolation, and PCR. While these methods are sufficient in most cases, each has their limitations. Cytology is a cost-effective and rapid approach that may be useful when traditional diagnostics are not feasible. The objective of this study was to evaluate the performance of cytology relative to histopathology and PCR for avian pox diagnosis in wild turkeys. Fifty wild turkeys were submitted for necropsy due to nodular skin lesions on unfeathered skin of the head. Of these, five had similar skin lesions on the unfeathered legs and 26 had plaques on the mucosa of the oropharynx or esophagus. Representative skin, oropharyngeal, and esophageal lesions from all birds were examined with cytology and histopathology. Skin lesions on the head of each bird were also tested for avian pox virus via PCR. Histopathology and PCR were equally sensitive in diagnosing avian pox from skin lesions on the head. There were no significant differences between cytologic and histopathologic diagnosis of avian pox from skin lesions on the head (sensitivity = 97.4%, specificity = 100.0%), legs (sensitivity = 75.0%, specificity = 100.0%), or from lesions in the oropharynx and esophagus (sensitivity of 62.5%). Similarly, there were no significant differences between PCR and cytology for diagnosis of pox viral skin lesions of the head. Relative to PCR detection of avian pox virus, cytology had a sensitivity of 90.0% and a specificity of 90.0%. These results suggest that cytology is a useful tool for diagnosis of avian pox in wild turkeys.

Accounting for tagging-to-harvest mortality in a Brownie tag-recovery model by incorporating radio-telemetry data.

The Brownie tag-recovery model is useful for estimating harvest rates but assumes all tagged individuals survive to the first hunting season; otherwise, mortality between time of tagging and the hunting season will cause the Brownie estimator to be negatively biased. Alternatively, fitting animals with radio transmitters can be used to accurately estimate harvest rate but may be more costly. We developed a joint model to estimate harvest and annual survival rates that combines known-fate data from animals fitted with transmitters to estimate the probability of surviving the period from capture to the first hunting season, and data from reward-tagged animals in a Brownie tag-recovery model. We evaluated bias and precision of the joint estimator, and how to optimally allocate effort between animals fitted with radio transmitters and inexpensive ear tags or leg bands. Tagging-to-harvest survival rates from >20 individuals with radio transmitters combined with 50-100 reward tags resulted in an unbiased and precise estimator of harvest rates. In addition, the joint model can test whether transmitters affect an individual's probability of being harvested. We illustrate application of the model using data from wild turkey, Meleagris gallapavo, to estimate harvest rates, and data from white-tailed deer, Odocoileus virginianus, to evaluate whether the presence of a visible radio transmitter is related to the probability of a deer being harvested. The joint known-fate tag-recovery model eliminates the requirement to capture and mark animals immediately prior to the hunting season to obtain accurate and precise estimates of harvest rate. In addition, the joint model can assess whether marking animals with radio transmitters affects the individual's probability of being harvested, caused by hunter selectivity or changes in a marked animal's behavior.