Chlamydia psittaci infection in horses: results of a prevalence survey and experimental challenge

Equine Psittacosis and the Emergence of Chlamydia psittaci as an Equine Abortigenic Pathogen in Southeastern Australia: A Retrospective Data Analysis

Chlamydia psittaci is an important zoonotic pathogen. Although primarily a pathogen of birds, from which infection can spillover into humans and other mammalian hosts, the importance of C. psittaci as a cause of equine reproductive loss and the risk of infection to humans in contact with infected horses are increasingly being recognised in Australia and elsewhere. Despite the risks to both human and equine health, C. psittaci infection in horses is incompletely understood. This study aimed to update and summarise cases of equine psittacosis in Australia in the period 2018-2022, thus addressing a knowledge gap relating to recent cases in this country. These cases were identified from the examination of records held by state and federal veterinary authorities and from a review of published cases. A total of 31 cases were identified. Spatial and temporal trends were identified, with cases being more prevalent in winter and spring and geographically restricted to Victoria and New South Wales. The results show that cases of equine reproductive loss due to C. psittaci are consistent and ongoing and demonstrate the importance of routinely considering C. psittaci in diagnostic investigations. The need for ongoing study to better understand this important zoonotic pathogen is evident.

Chlamydia psittaci infection as a cause of respiratory disease in neonatal foals

BACKGROUND

During 2016-2018, 15 critically ill neonatal foals with acute respiratory distress associated with Chlamydia psittaci infection were presented to three referral hospitals in New South Wales. Chlamydia psittaci has not previously been associated with the development of neonatal respiratory disease.

OBJECTIVES

To investigate and describe the clinical features and outcome of C. psittaci infection in neonatal foals.

STUDY DESIGN

Multicentre retrospective case series.

METHODS

The clinical, clinicopathological, necropsy and histological features of 15 foals with confirmed C. psittaci infection were reviewed and reported.

RESULTS

Thirteen foals with C. psittaci infection died or were subjected to euthanasia within 36 h of hospitalisation and two foals survived to discharge. Findings during post-mortem examination of nonsurviving foals included bronchopneumonia, pulmonary congestion, hepatic congestion and hepatic inflammation. Detection of C. psittaci was achieved using polymerase chain reaction (PCR) testing of swabs of nasal secretions (4/6) and rectal mucosa (5/7) from live foals, lung tissues of foals at necropsy (11/14) and foetal membranes (4/5).

MAIN LIMITATIONS

Small numbers of confirmed cases of neonatal C. psittaci infection and inconsistent sampling methods.

CONCLUSIONS

Chlamydia psittaci should be considered a differential diagnosis for neonatal foals with signs of severe systemic disease, including equine neonatal acute respiratory distress syndrome (EqNARDS). Chlamydia psittaci is a zoonotic pathogen and a personal protective equipment (PPE) should be worn for the management of foals with suspected or confirmed infection.

Detection of chlamydiae from the upper respiratory tract of healthy and diseased draught equines

The present investigation was conducted to study the prevalence and molecular characterization of chlamydiae associated with the respiratory infections of equines in the Sub-Himalayan region of India. Equine nasal swab samples (119) from 20 diseased and 99 apparently healthy equines were collected and tested by family Chlamydiaceae specific nested PCR based on ompA gene, besides 89 serum samples for AGPT. The molecular characterization of chlamydial species/strains was done by analyzing variation in VD II region of ompA gene. The chlamydia infections were detected in 48.74% of the nasal swabs (55% in diseased and 47.47% in apparently healthy animals) by nested PCR. Prevalence of two genetically variant strains of Chlamydia abortus and a single strain of Chlamydia psittaci was detected. AGPT showed 4.49% seropositive equines. High prevalence of chlamydiae was found among equines in the Sub-Himalayan region of India in Himachal Pradesh in both healthy and diseased equines.

Molecular and serological detection of Leishmania spp. in horses from an endemic area for canine visceral leishmaniasis in southeastern Brazil

ABSTRACT: This study aimed to verify the occurrence of Leishmania spp. and Leishmania (Leishmania) infantum in horses from a visceral leishmaniasis endemic area in Brazil. DNA samples from blood and conjunctival swab (CS) were tested by PCR and Indirect Immunofluorescence Antibody Test (IFAT). Although none of the horses was clinically sick, animals infected by Leishmania spp. were found and some could be characterized as infected by L. (L.) infantum. From 40 horses, 100% of the animals were positive by blood PCR, 90% (36/40) by CS PCR, and 2.5% (01/40) in serodiagnosis, by IFAT. Six from these 40 horses were L. (L.) infantum positive by blood PCR. Direct sequencing and analysis of amplicons resulted in a sequence to evolutionary analysis. Results indicate the presence of Leishmania spp. and L. (L.) infantum infecting healthy horses in Brazil. The presence of Leishmania spp. and L. (L.) infantum DNA in asymptomatic horses suggests that they can be important reservoirs of these parasites, a highly relevant finding for the epidemiological surveillance of the diseases they cause.

Detection of Chlamydophila caviae and Streptococcus equi subsp. zooepidemicus in horses with signs of rhinitis and conjunctivitis

At a stud farm of Trakehner horses, all 33 foals of a birth cohort developed conjunctivitis and serous to muco-purulent rhinitis, and 7 older horses showed recurrent signs of conjunctivitis. Examination of nasal and conjunctival swabs by bacterial and cell culture, as well as real-time PCR, ArrayTube microarray analysis and DNA sequencing led to the identification of Chlamydophila (C.) caviae (first description in horses) and Streptococcus (S.) equi subsp. zooepidemicus. We presume a synergistic effect associated with these two agents by hypothesising that primary lesions were set by C. caviae and subsequently aggravated by Streptococcus equi subsp. zooepidemicus. Indications supporting this assumption include (i) the conjunctivitis caused by mono-infection with C. caviae, (ii) recurrent clinical symptoms in the affected animals, and (iii) the absence of a sustained clinical effect of antibiotic therapy with trimethoprim-sulfonamide, enrofloxacin and amoxicillin. The detection of C. caviae in horses raises questions about the significance and natural host range of this agent.

Unusual transmission route of Lymphogranuloma venereum; following sexual contact with a female donkey

Here, we present a 20-year-old man who presented with painful inguinal and femoral masses. He gave a history of sexual contact with a mare 14 days before his recent illness. He was diagnosed with lymphogranuloma venereum based on the histopathological findings and a high titre of IgG (1:1400).

Chlamydophila spp. infection in horses with recurrent airway obstruction: similarities to human chronic obstructive disease

Background

Recurrent airway obstruction (RAO) in horses is a naturally occurring dust-induced disease mainly characterized by bronchiolitis which shows histological and pathophysiological similarities to human chronic obstructive pulmonary disease (COPD). In human COPD previous investigations indicated an association with Chlamydophila psittaci infection. The present study was designed (1) to clarify a possible role of this infectious agent in RAO and (2) to investigate the suitability of this equine disorder as a model for human COPD.

Methods

Clinico-pathological parameters of a total of 45 horses (25 horses with clinical signs of RAO and 20 clinically healthy controls) were compared to histological findings in lung tissue samples and infection by Chlamydiaceae using light microscopy, immunohistochemistry, and PCR.

Results

Horses with clinical signs of RAO vs. controls revealed more inflammatory changes in histology (p = 0.01), and a higher detection rate of Chlamydia psittaci antigens in all cells (p < 0.001) and bronchiolar epithelial cells alone (p < 0.001) by immunohistochemistry. The abundance of chlamydial inclusions increased with the severity of disease. PCR was positive in 60% of horses with RAO vs. 45% of the controls (p = 0.316). OmpA sequencing identified Chlamydophila psittaci (n = 9) and Chlamydophila abortus (n = 13) in both groups with no significant differences. Within the group of clinically healthy horses subgroups with no changes (n = 15) and slight inflammation of the small airways (n = 5) were identified. Also in the group of animals with RAO subgroups with slight (n = 16) and severe (n = 9) bronchiolitis could be formed. These four subgroups can be separated in parts by the number of cells positive for Chlamydia psittaci antigens.

Conclusion

Chlamydophila psittaci or abortus were present in the lung of both clinically healthy horses and those with RAO. Immunohistochemistry revealed acute chlamydial infections with inflammation in RAO horses, whereas in clinically healthy animals mostly persistent chlamydial infection and no inflammatory reactions were seen. Stable dust as the known fundamental abiotic factor in RAO is comparable to smoking in human disease. These results show that RAO can be used as a model for human COPD.

High prevalence of chlamydial (Chlamydophila psittaci) infection in fetal membranes of aborted equine fetuses

Seventy-seven cases of equine abortion from 49 Hungarian farms that occurred between 1998 and 2000 were investigated for the presence of chlamydiae by immunohistochemistry, PCR and/or MZN staining. Evidence of the presence of these bacteria was obtained in 64 cases (83.1%) from 41 (83.7%) different farms. Partial ompA gene sequencing of PCR products revealed that the agent was Chlamydophila psittaci. Based on the findings of microbial diagnosis, pathology and case history, chlamydial infection was considered to be the most likely cause of abortion in at least 11 (14.3%) cases. In the remaining 53 Chlamydophila-positive cases, either other bacterial and viral agents (n = 22 or 28.6%) as well as non-infectious factors (n = 14 or 18.2%) were identified as more probable primary causes of disease, or the role of chlamydiae remained unclear because lesions in fetuses and fetal membranes were absent (n = 17 or 22.1%). When chlamydial antigen was detected in aborted equine placental tissue using immunohistochemistry it was seen only in the chorionic epithelial cells, but not in other parts of the fetal membranes nor in any of the fetal tissues. In conclusion, chlamydial infection of the genital tract should be considered a possible factor in equine reproductive disorders.

Chlamydia and Chlamydiales: more than meets the eye

This review summarizes the dramatic changes that have occurred in the taxonomy of bacteria known as Chlamydia. Best known for the diseases they cause in humans, these intracellular bacteria also comprise many species that are responsible for a wide variety of clinically and economically important diseases in livestock and companion animals. The old taxonomy grouped most of these species into C. psittaci because systematic methods for routinely distinguishing them were not available. DNA-based testing methods are now available that distinguish different chlamydial families, genera, and species. This summary reviews these tests and a number of oligonucleotide primers that distinguish these groups using PCR and PCR-RFLP. DNA-based methods are also being used to discover new families of chlamydia-like bacteria, at least one of which is responsible for abortion in cattle (Waddlia chondrophila). This review summarizes the pathogenic roles of the Chlamydiaceae, new families, and individual species within the order Chlamydiales. These discoveries create opportunities for veterinarians to carry out epidemiological studies of chlamydiae that previously were not possible.