An Unusual Outbreak of Chlamydiosis in Commercial Turkeys Involving the Nasal Glands

Complete genome sequence of Chlamydia psittaci АМК-16, isolated from a small ruminant in the Middle Volga Region, Russia

We report the complete genome sequence of the Chlamydia psittaci АМК-16, recovered from the aborted caprine fetus during a case of chlamydia infection. This 1,152,497-bp genome with 7,552-bp cryptic plasmid provides novel insights into the genetic diversity of chlamydia agent strains particularly those causing the infection in small ruminants.

Whole genome sequencing characteristics of Chlamydia psittaci caprine AMK-16 strain, a promising killed whole cell veterinary vaccine candidate against chlamydia infection

Chlamydia psittaci is a primary zoonotic pathogen with a broad host range causing severe respiratory and reproductive system infection in animals and humans. To reduce the global burden of C. psittaci-associated diseases on animal welfare and health and to control the pathogen spread in husbandry, effective vaccines based on promising vaccine candidate(s) are required. Recently, the caprine C. psittaci AMK-16 strain (AMK-16) demonstrated a high level of protection (up to 80-100%) in outbred mice and pregnant rabbits immunized with these formaldehyde-inactivated bacteria against experimental chlamydial wild-type infection. This study investigated the molecular characteristics of AMK-16 by whole-genome sequencing followed by molecular typing, phylogenetic analysis and detection of main immunodominant protein(s) eliciting the immune response in mouse model. Similarly to other C. psittaci, AMK-16 harbored an extrachromosomal plasmid. The whole-genome phylogenetic analysis proved that AMK-16 strain belonging to ST28 clustered with only C. psittaci but not with Chlamydia abortus strains. However, AMK-16 possessed the insert which resulted from the recombination event as the additional single chromosome region of a 23,100 bp size with higher homology to C. abortus (98.38-99.94%) rather than to C. psittaci (92.06-92.55%). At least six of 16 CDSs were absent in AMK-16 plasticity zone and 41 CDSs in other loci compared with the reference C. psittaci 6BC strain. Two SNPs identified in the AMK-16 ompA sequence resulted in MOMP polymorphism followed by the formation of a novel genotype/subtype including three other C. psittaci strains else. AMK-16 MOMP provided marked specific cellular and humoral immune response in 100% of mice immunized with the inactivated AMK-16 bacteria. Both DnaK and GrpE encoded by the recombination region genes were less immunoreactive, inducing only a negligible T-cell murine immune response, while homologous antibodies could be detected in 50% and 30% of immunized mice, respectively. Thus, AMK-16 could be a promising vaccine candidate for the development of a killed whole cell vaccine against chlamydiosis in livestock.

A comprehensive review on avian chlamydiosis: a neglected zoonotic disease

Avian chlamydiosis is one of the important neglected diseases with critical zoonotic potential. Chlamydia psittaci, the causative agent, affects most categories of birds, livestock, companion animals, and humans. It has many obscured characters and epidemiological dimensions, which makes it unique among other bacterial agents. Recent reports on transmission from equine to humans alarmed the public health authorities, and it necessitates the importance of routine screening of this infectious disease. High prevalence of spill-over infection in equines was associated with reproductive losses. Newer avian chlamydial species are being reported in the recent years. It is a potential biological warfare agent and the disease is an occupational hazard mainly to custom officers handling exotic birds. Prevalence of the disease in wild birds, pet birds, and poultry causes economic losses to the poultry industry and the pet bird trade. Interestingly, there are speculations on the ‘legal’ and ‘illegal’ bird trade that may be the global source of some of the most virulent strains of this pathogen. The mortality rate generally ranges from 5 to 40% in untreated cases, but it can sometimes be higher in co-infection. The intracellular lifestyle of this pathogen makes the diagnosis more complicated and there is also lack of accurate diagnostics. Resistance to antibiotics is reported only in some pathogens of the Chlamydiaceae family, but routine screening may assess the actual situation in all pathogens. Due to the diverse nature of the pathogen, the organism necessitates the One Health partnerships to have complete understanding. The present review focuses on the zoonotic aspects of avian chlamydiosis with its new insights into the pathogenesis, transmission, treatment, prevention, and control strategies. The review also briefs on the basic understandings and complex epidemiology of avian chlamydiosis, highlighting the need for research on emerging one health perspectives.

Chlamydiosis in a Gouldian Finch (Erythrura gouldiae)

Avian chlamydiosis is an infection caused by obligate intracellular and Gram-negative bacteria belonging to the family Chlamydiaceae and has been reported in more than 450 avian species distributed in 30 orders. In particular, a high prevalence of infection has been demonstrated in wild passerine populations, including both asymptomatic and clinically ill individuals, suggesting a role of these avian species as important carriers. In May 2018, avian chlamydiosis was diagnosed in a 1-year-old male Gouldian finch (Erythrura gouldiae) at the Turlock Branch of the California Animal Health and Food Safety Laboratory System. The bird belonged to an outdoor aviary with mixed avian species, including Gouldian finches, doves (Geopelia cuneata and Spilopelia chinensis), and psittacines (Aratinga, Psittacula, Pyrrhura, and Trichoglossus sp.). Severe respiratory distress and mortality were noted among the finches. Gross and histopathologic lesions were concentrated in the liver and spleen, with a mild involvement of the upper respiratory tract. Chlamydia spp. were detected in the spleen and kidney by real-time PCR and were further confirmed by immunohistochemistry. Subsequently, Chlamydia psittaci was isolated from the liver and spleen and characterized as a CP3-like strain (genotype B). In addition, viral particles compatible with circovirus were identified in the liver by direct electron microscopy. To the authors' knowledge, this is the first report of avian chlamydiosis with hepatic viral particles consistent with circovirus infection in a Gouldian finch.

Rotavirus A Associated with Clinical Disease and Hepatic Necrosis in California Pigeons (Columba livia domestica)

Retrospective analysis of pigeon necropsy submissions to the California Animal Health and Food Safety Laboratory System from 2000 to 2018 revealed 14 submissions diagnosed with rotavirus A hepatic necrosis or "reoviruslike" viral hepatitis. Nine of the 14 submissions (64%) occurred in 2018. Submissions were racing pigeons and squab breeders from flocks with increased mortality. Juvenile and adult pigeons were submitted with a history of depression, diarrhea, regurgitation, labored breathing, and weakness. Flock morbidity peaked at 80% and mortality at 28%. The most consistent findings on postmortem examination were variably congested, mottled, and enlarged livers and spleens. Microscopically, mild to severe hepatic necrosis was observed with variable bile duct hyperplasia, sinusoidal congestion, hemosiderosis, and portal lymphoplasmacytic inflammation. Rotavirus A was detected in hepatocytes and inflammatory cells by immunohistochemistry. Negative-stain electron microscopy identified viral particles consistent with a member of Reoviridae in all negatively stained liver homogenates. Eleven cases were analyzed by reverse transcriptase-PCR targeting rotavirus A viral protein (VP) 6 and VP7 genes. Subsequent phylogenetic analysis of the VP6 and VP7 sequences compared to published Chinese, Nigerian, and German rotavirus A VP6 and VP7 sequences demonstrated the formation of two and three distinct clades, respectively. To the authors' knowledge, rotavirus A hepatic necrosis in pigeons has not been previously reported in the United States and represents a significant emerging disease for the pigeon industry due to the potential for high flock mortality and lost production.

The Nasal Gland in Turkeys (Meleagris gallopavo): Anatomy, Histology, and Ultrastructure

This study provides a detailed description of the major morphoanatomic and ultrastructural features of the nasal gland in turkeys. In this avian species, nasal or salt glands are bilateral, pale pink, elongated to spindle-shaped, serous, tubuloalveolar structures, with a mean length ranging from 0.64 ± 0.15 cm in poults of 4 days of age to 2.15 ± 0.17 cm at 22 weeks. Instead of having a supraorbital location as commonly seen in waterfowl and other avian species, these glands run underneath the lacrimal, frontal, and nasal bones in turkeys. The reference point for sample collection for histologic examination is just before the rostral edge of the eyelid. Each gland adheres to the surrounding bone through a thick capsule of dense connective tissue merging with the skull periosteum. Histologically, the salt gland consists of secretory tubuloalveolar structures, lined by cuboidal epithelial cells with a central canaliculus and ducts. There are small and large ducts lined by a bilayered epithelium consisting of large apical columnar secretory cells occasionally admixed with rare cuboidal cells. These cells are periodic acid Schiff negative and slightly Alcian blue positive. Both alveolar and secretory ductal cells contain slightly electrondense granular vesicles, highly folded lateral surfaces, and large numbers of mitochondria, characteristic of ion-transporting epithelia. This study provides valuable information for the accurate identification and localization of the nasal gland during necropsy, as well as its correct histologic interpretation, ultimately improving our understanding of the role of this gland in the pathophysiology of specific diseases in turkeys.

Psittacosis Outbreak among Workers at Chicken Slaughter Plants, Virginia and Georgia, USA, 2018

During August–October, 2018, an outbreak of severe respiratory illness was reported among poultry slaughter plant workers in Virginia and Georgia, USA. A multiorganizational team investigated the cause and extent of illness, determined that the illness was psittacosis, and evaluated and recommended controls for health hazards in the workplace to prevent additional cases.

Cross-sectional study on Chlamydiaceae prevalence and associated risk factors on commercial and backyard poultry farms in Mexico

Chlamydiaceae infections in poultry are mainly due to Chlamydia psittaci and Chlamydia gallinacea. While C. psittaci has long been known to affect birds and to have zoonotic potential, C. gallinacea is a newly described species that has been found to be widespread in chickens. As no data were available regarding the presence of Chlamydiaceae in Mexican poultry, a cross-sectional survey to detect the presence of Chlamydiaceae on commercial and backyard farms was carried out in eight federal states of Mexico with a high poultry density. Individual cloacal swabs were collected on 14 large-scale commercial poultry farms with controlled environment houses, 23 large-scale commercial poultry farms with open-sided houses, and 16 backyard farms. Samples were tested using a specific Chlamydiaceae real-time PCR technique. Chlamydial species were subsequently identified by a species-specific real-time PCR method. Information on potential risk factors was collected through a questionnaire. Logistic regression was performed to identify risk factors associated with Chlamydiaceae-positive results at the farm level on commercial farms. For backyard farms, a mixed-effect logistic regression model was used to consider information collected either at the animal or at the farm level. Overall, 7.1 % (n = 1/14) of controlled environment commercial farms, 26.1 % (n = 6/23) of open-sided commercial farms, and 75.0 % (n = 12/16) of backyard farms were Chlamydiaceae-positive. Apparent prevalence increased inversely to the level of confinement (controlled environment vs open-sided poultry houses vs backyards). Chlamydia gallinacea was the only chlamydial species detected. On commercial farms, egg-laying hen flocks had 6.7 times higher odds of being Chlamydiaceae-infected than broilers flocks (OR = 6.7, 95 % CI: 1.1-44.3, p = 0.04). On backyard farms, two variables were significantly associated with Chlamydiaceae infection: the lack of antibiotic use (OR = 8.4, 95 % CI: 1.84-38.49, p = 0.006), and an impaired health status (OR=8.8, 95 % CI: 1.9-38.9, p = 0.004). Further studies should be carried out to investigate the impact of C. gallinacea infection on egg quality and production performance in egg-laying hen flocks.