Taking a rational approach in the treatment of avian mycobacteriosis

MORTALITY TRENDS FOR BUDGERIGARS (MELOPSITTACUS UNDULATUS) HOUSED IN A WALK-THROUGH AVIARY IN A ZOO IN NORTH AMERICA, 2009-2019

Many zoos in North America feature walk-through exhibits that allow members of the public to interact with psittacine species, as these exhibits are popular with guests and can generate additional revenue. There is limited research available on the life expectancy and common causes of mortality of psittacines when group-housed in aviaries. This study compiled data on 496 budgerigar (Melopsittacus undulatus) mortalities at a walk-through aviary at a North American zoo from March 2009 to March 2019, including histopathology on 62 tissue sets collected post mortem, and gross necropsy data for 163 birds deceased from March 2015 to March 2019. The mean age at death or euthanasia of all fledged birds from 2015 to 2019 was 3.57 ± 1.58 yr. The most common causes of death or euthanasia found on gross necropsy were granulomatous disease (39.2%), trauma (16.0%), and Macrorhabdus ornithogaster (13.5%). The most common histologic finding was M. ornithogaster, described as the primary pathologic finding in 31.7% of submitted tissue sets, and recorded as a secondary pathologic finding in 53.2% of submitted tissue sets. Mycobacterial disease was the primary pathologic finding in 25.3% of submitted tissue sets, and was recorded as an additional pathologic finding in 35.4% of submitted tissue sets.

Monitored therapy of sporadic mycobacteriosis caused by Mycobacterium genavense in Atlantic canaries (Serinus canaria) and Bengalese finch (Lonchura striata)

Introduction

Mycobacteriosis is a significant disease of companion and wild birds which causes emaciation and widely distributed lesions, as well as being a potential zoonosis. Its primary aetiological agents in birds are Mycobacterium avium subsp. avium and the fastidious Mycobacterium genavense. This study monitored the therapy of birds naturally infected with Mycobacterium genavense to gain understanding of its effectiveness and the interrelation of co-infections with the disease course and pharmacotherapy.

Material and Methods

Five Atlantic canaries (Serinus canaria) and one Bengalese finch (Lonchura striata) with tentative diagnoses of mycobacteriosis resulting from M. genavense infection were treated twice daily with clarithromycin at 40 mg/kg, ethambutol at 30 mg/kg, and moxifloxacin at 10 mg/kg for 6 months. Two canaries were also found to be carriers of Cryptosporidium galli. Mycobacteria in faecal samples of all birds were investigated by bacterioscopy and quantitative PCR.

Results

Molecular tests yielded positive results for up to four months after treatment initiation for M. genavense and Cryptosporidium, but microscopy failed to detect the latter after four weeks in specimens from one canary. Co-infections with polyomavirus (in all birds) and circovirus and bornavirus (in canaries) were diagnosed. Two birds died during treatment and one was euthanised because of other disease, 1 month after treatment completion. Three canaries were in relatively good health a year after treatment.

Conclusion

Canary circovirus and polyomavirus co-infection may suppress the immune system and this may facilitate the development of mycobacteriosis. The set of drugs used led to the complete cure of mycobacteriosis in three canaries. In one bird the disease returned. Clarithromycin was the active drug against C. galli. Molecular methods serve well to monitor mycobacteriosis therapy and identify M. genavense and C. galli carriage.

Retrospective Review of Mycobacterial Conjunctivitis in Cockatiels (Nymphicus hollandicus)

The etiologic disease organism responsible for causing mycobacteriosis in avian species is an acid-fast gram-positive bacterium. This bacterium causes granulomatous disease in various internal organs, but in cockatiels (Nymphicus hollandicus) it has been commonly identified within the conjunctival tissues. Twenty-six cases of mycobacterial conjunctivitis in cockatiels were diagnosed through histopathologic assessment of diseased tissue samples, Fite acid-fast staining, and polymerase chain reaction in this retrospective study. Clinicians who saw these cases were contacted, and information was obtained regarding recommended treatment protocols prescribed for the patients, the Mycobacterium species identified, and case outcomes. All patients in this retrospective study had a biopsy performed on the affected conjunctival tissue, and because of the small size of the patients, this excisional biopsy removed the affected tissue in its entirety or significantly debulked the lesion. Of the 26 cases, 10 were lost to follow-up, 4 were euthanatized, 7 died, and 5 were alive at the time this information was submitted for publication.

Treatment of a mycobacterial infection in an Eastern Long-neck turtle (Chelodina longicollis)

BACKGROUND

Mycobacterial infections are uncommonly diagnosed in reptiles. These infections are often systemic, chronic, and well advanced before presentation and diagnosis. Turtles, both marine and freshwater, appear to have a higher prevalence of the disease than other reptiles, perhaps because of their aquatic environment.

CASE REPORT

An Eastern Long-neck turtle (Chelodina longicollis) was diagnosed with an apparently localised mycobacterial infection in the right foot. Biopsy, culture and PCR were used to make the diagnosis. Treatment with clarithromycin and rifampicin given orally for 9 months appeared to successfully resolve the infection.

CONCLUSION

Antemortem diagnosis is difficult although molecular diagnostic techniques are improving the rates of diagnosis. Treatment of mycobacteria is lengthy, difficult and challenging to the patient, the owner and the veterinarian. For this reason, and because of the potential for zoonotic infection, it is infrequently undertaken.

Case Study and Attempt of Treatment of Mycobacteriosis Caused by Mycobacterium avium in a Parental Flock of Meat-Breed Pigeons

Mycobacteriosis caused by Mycobacterium avium subsp. avium was observed in a parental loft of 70 meat-breed pigeons. It was decided to undertake treatment as the birds represented a substantial value to the owner. A multiagent therapy using azithromycin, marbofloxacin, and ethambutol was administered. After 4 mo of therapy, the desired results were not obtained. At the end of treatment, the birds were in poor general condition, with white blood cells above 20 g/L, and after clutching, 2-yr-old and older birds were euthanatized. Overall, postmortem lesions were found in 17 out of 49 necropsied individuals. Slide agglutination tests with a M. avium subsp. avium lysate were conducted in all examined pigeons. In 28 pigeons, blood count was conducted once a month during therapy, while in 24 pigeons, a tuberculin sensitivity test was conducted before the planned euthanatization. The tuberculin sensitivity test did not prove useful in the diagnosis of ill individuals. Slide agglutination yielded positive results in only four birds, all of which also had postmortem lesions. Blood count in a large number of cases allowed distinguishing between ill and healthy individuals, which was used for subsequent selection. The comparison of cultured strains with the (CCG)4-based PCR method showed the variation of M. avium isolates up to a maximum of 30%. The described case proves that the treatment of mycobacteriosis in pigeon flocks is not effective, mainly due to the high resistance to M. avium subsp. avium. In addition, therapy may contribute to an even greater increase in mycobacterial resistance to antibiotics, which may pose a potential risk to public health.

Isolation, Identification, and Characterization of a New Highly Pathogenic Field Isolate of Mycobacterium avium spp. avium

Avian tuberculosis is a chronic, contagious zoonotic disease affecting birds, mammals, and humans. The disease is most often caused by Mycobacterium avium spp. avium (MAA). Strain resources are important for research on avian tuberculosis and vaccine development. However, there has been little reported about the newly identified MAA strain in recent years in China. In this study, a new strain was isolated from a fowl with symptoms of avian tuberculosis by bacterial culture. The isolated strain was identified to be MAA by culture, staining, and biochemical and genetic analysis, except for different colony morphology. The isolated strain was Ziehl-Zeelsen staining positive, resistant to p-nitrobenzoic acid, and negative for niacin production, Tween-80 hydrolysis, heat stable catalase and nitrate production. The strain had the DnaJ gene, IS1245, and IS901, as well. Serum agglutination indicated that the MAA strain was of serotype 1. The MAA strain showed strong virulence via mortality in rabbits and chickens. The prepared tuberculin of the MAA strain had similar potency compared to the MAA reference strain and standard tuberculin via a tuberculin skin test. Our studies suggested that this MAA strain tends to be a novel subtype, which might enrich the strain resource of avian tuberculosis.

Infectious Diseases

The chapter describes bacerial, viral, parasitic and fungal infections commonly detected in pet birds. The chapter includes history, etiology, susceptible hosts, transmission, pathogenesis, clinical symptoms, lesion, diagnosis, zoonosis, Treatment and control strategy of Tuberculosis, Salmonellosis, Chlamydiosis, Campylobacteriosis, Lyme disease, other bacterial infection, Newcastle disease, Avian Influenza infection, West Nile Virus infection, Usutu virus infection, Avian Borna Virus infection, Beak and feather disease, other viral infection, Toxoplasmosis, Giardiasis, Cryptosporidiosis, other parasitic infection, Cryptococcosis, Aspergillosis, Other fungal infections.

Multidrug therapy of Mycobacterium avium subsp. avium infection in experimentally inoculated budgerigars (Melopsittacus undulatus)

The aim of the study was to determine whether the four-month experimental therapy of mycobacteriosis in budgerigars may cause a complete recovery. A group of nine budgerigars was infected with a Mycobacterium avium subsp. avium isolate with proven pathogenicity for budgerigars. Five weeks post-inoculation, multidrug therapy was started. Another group comprising six birds received the same treatment but no infection, and the third group also comprising six birds was kept without infection or treatment as a control. The adopted antibiotic regimen included clarithromycin 61 mg/kg b.w., moxifloxacin 25 mg/kg b.w. and ethambutol 60 mg/kg b.w. administered by crop gavage every 12 h for 18 weeks. Despite a significant improvement in the condition of the infected, treated birds, the four-month therapy was not sufficient for the complete recovery of all.

Evaluation of Multidrug Therapy With Azithromycin, Rifampin, and Ethambutol for the Treatment of Mycobacterium avium subsp avium in Ring-neck Doves (Streptopelia risoria): An Uncontrolled Clinical Study

An uncontrolled clinical study was conducted to evaluate the efficacy of a multidrug protocol in 16 ring-neck doves ( Streptopelia risoria ) from a flock naturally infected with Mycobacterium avium subsp avium. The doves were considered infected on the basis of a high prevalence of infection in a group of 29 birds that were euthanatized from the same flock and clinical signs and pathologic results consistent with infection in the remaining birds. All birds were treated with azithromycin (43 mg/kg), rifampin (45 mg/kg), and ethambutol (30 mg/kg) administered orally once daily for 180 days. Five birds died during treatment and were confirmed positive for mycobacteriosis on postmortem examination. Of the remaining 11 birds, infection and disease were present in 9 (81.8%) at the end of the treatment. Postmortem investigation showed that 2 mycobacterial isolates were resistant to ethambutol, intermediately sensitive to rifampin, and sensitive to azithromycin. Microscopic examination of liver sections equivalent of those that would be taken for biopsy showed that biopsy as a method of monitoring birds for treatment success had poor sensitivity. Toxicity associated with drug therapy was not observed in these doves nor in 6 outwardly healthy ring-neck doves exposed to the same treatment. The results of this study showed that this protocol of azithromycin, rifampin, and ethambutol has poor efficacy when administered for 180 days for treatment of doves infected with M avium subsp avium.