Molecular epidemiology of mycobacteriosis in wildlife and pet animals

Evolution of Tuberculosis Pathogenesis

Mycobacterium tuberculosis is a globally distributed, lethal pathogen of humans. The virulence armamentarium of M. tuberculosis appears to have been developed on a scaffold of antiphagocytic defenses found among diverse, mostly free-living species of Mycobacterium. Pathoadaptation was further aided by the modularity, flexibility, and interactivity characterizing mycobacterial effectors and their regulators. During emergence of M. tuberculosis, novel genetic material was acquired, created, and integrated with existing tools. The major mutational mechanisms underlying these adaptations are discussed in this review, with examples. During its evolution, M. tuberculosis lost the ability and/or opportunity to engage in lateral gene transfer, but despite this it has retained the adaptability that characterizes mycobacteria. M. tuberculosis exemplifies the evolutionary genomic mechanisms underlying adoption of the pathogenic niche, and studies of its evolution have uncovered a rich array of discoveries about how new pathogens are made. Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Disseminated Mycobacterium genavense infection in a guinea pig (Cavia porcellus): a case report

Background

Mycobacteria are found in many environmental conditions and infect a variety of species, including rodents and rabbits. Guinea pigs are used experimentally as a model for Mycobacterium tuberculosis, but natural mycobacteriosis in guinea pigs has not been reported.

Case presentation

A 1.5-year-old female guinea pig was found acutely deceased with no premonitory illness. On gross post-mortem examination, multifocal to coalescing, raised, firm, pale tan nodules with discrete, irregular margins were noted over the surfaces of all lung lobes. Histopathology revealed nodules composed of clustered foamy macrophages and multinucleated giant cells containing numerous bacterial rods. Similar bacteria-laden macrophages were noted within sections of the liver, heart, palpebral conjunctiva, duodenum, and cecum. Polymerase chain reaction was performed on tissues collected during post-mortem examination. The 16S rRNA gene product was sequenced and was identical to the Mycobacterium genavense type strain.

Conclusions

To the best of the author’s knowledge, this report details the first documented case of Mycobacterium genvaense infection in a guinea pig and a follow up investigation of close-contact animals. Given their experimental susceptibility and this clinical case report, mycobacteriosis should be considered as a differential in guinea pigs exhibiting weight loss in the absence of other clinical signs. With the potential for zoonotic transmission in immunosuppressed individuals, precautions should be taken to safeguard human health in cases of guinea pigs with suspected M. genavense infection.

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.

Mycobacterial Airsacculitis Caused by Mycobacterium fortuitum in a Southern Rockhopper Penguin (Eudyptes chrysocome)

A 21-year-old male southern rockhopper penguin (Eudyptes chrysocome) was presented with a chronic history of intermittently decreased appetite, lethargy, and regurgitation. On the external physical examination, the bird was determined to be in fair-to-thin body condition with the complete blood count and plasma chemistry panel being largely unremarkable. Full-body radiographic images were considered normal, and gastroscopy showed only mild gastritis and duodenitis. The penguin was euthanatized shortly thereafter due to acute onset of respiratory distress. During the gross necropsy examination, the bird had severe airsacculitis with thick, yellow-to-tan, moist granular plaques adhering to the surface of many air sacs, as well as regional contiguous pneumonia. Intralesional acid-fast bacilli were observed in histologic sections of air sac tissue, and polymerase chain reaction of the affected air sacs was positive for Mycobacterium fortuitum. This clinical case study describes mycobacteriosis in a sub-Antarctic penguin and to the best of the authors' knowledge, the first reported isolation of M fortuitum from a penguin.

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.

Longitudinal social network analysis of avian mycobacteriosis incidence in a large population of zoo birds

The goal of this study was to evaluate longitudinal patterns of avian mycobacteriosis spread through a social network. Specifically, we wanted to determine whether the patterns of connectivity over time can predict future infections, and whether this pattern can distinguish between different sources of infection. The study population included 13,409 individuals nested in a larger population of birds that were closely monitored in zoological facilities for over 22 years (1992-2014). A retrospective cohort study design and social network connectivity were used to estimate the association between exposure to an infected bird, and development of mycobacteriosis. Avian mycobacteriosis was diagnosed from histopathology and network connectivity was defined by enclosure histories over discrete time periods. Single-variable and multivariable longitudinal, mixed effects logistic regression models examined whether exposure to infected birds, both directly- and indirectly-connected, was associated with development of mycobacteriosis at the next time step. Our adjusted model showed an increased odds of developing mycobacteriosis (odds ratio = 2.15; 95 % CI: 1.48-3.12; p < 0.001) for birds that were directly exposed (i.e., housed in the same aviary) to another infected bird, compared to those with no exposure. Exposure to a positive, indirectly-connected bird at a previous time step was independently associated with an increased risk of mycobacteriosis (odds ratio = 1.56; 95 % CI: 1.11-2.19). This association persisted in adjusted models even when the indirect contacts were housed in distinctly different aviaries and never had contact with the subject of interest or its environment. Adjusted, risk-stratified models further characterized the type of exposure that increased the risk of avian mycobacteriosis. Birds that were exposed in small aviaries were more likely to develop mycobacteriosis than those exposed in larger aviaries and those with no exposure. The lesion distribution and species of the contact (same species versus different species) were also significant predictors of disease risk. Some findings were sensitive to model variation of time divisions and initiation time. Our study shows avian mycobacteriosis spread through the social network in quantifiable and discernable patterns. We provide empirical evidence that a contagious process drives some of the observed infection, but we also show low transmissibility based on sustained patterns of low incidence over time even when large groups of birds are exposed. Targeted risk mitigation efforts based on the characteristics of the exposure may be effective at reducing risk of avian mycobacteriosis while enhancing population sustainability.

Non-tuberculous Mycobacteria can Cause Disseminated Mycobacteriosis in Cats

Mycobacteriosis caused by non-tuberculous mycobacteria (NTM) is a rising concern in human medicine both in immunocompromised and immunocompetent patients. In cats, mycobacteriosis caused by NTM is considered mostly to be a focal or dermal infection, with disseminated disease mostly caused by Mycobacterium avium. We describe three cases of disseminated mycobacteriosis in cats, caused by Mycobacterium malmoense, Mycobacterium branderi/shimoidei and M. avium, with no identified underlying immunosuppression. In all cases, extracellular mycobacteria were seen in the pulmonary epithelium, intestinal lumen and glomerular tufts, which could affect the shedding of the organism. The present study highlights the importance of mycobacteriosis as a differential even in immunocompetent animals. Considering the close relationship of owners and pets and the potential presence of free mycobacteria in secretions, cats should be considered as a possible environmental reservoir for mycobacteria.

MYCOBACTERIUM INTRACELLULARE INFECTION CAUSING A RETROPERITONEAL MASS IN A BINTURONG (ARCTICTIS BINTURONG)

A 19-yr-old castrated male binturong ( Arctictis binturong ) with a history of recurrent pyogranulomatous panniculitis, lymphangitis, and dermatitis was presented for evaluation of hyporexia and tenesmus. A large caudal abdominal mass was palpated on physical examination. On ultrasound, the mass encircled and obstructed the left ureter, resulting in hydroureter and hydronephrosis. The animal was euthanized, and necropsy revealed a large retroperitoneal pyogranuloma with acid-fast organisms identified in both the mass and the perineal skin. The acid-fast organisms within the retroperitoneal mass were identified as Mycobacterium intracellulare by PCR. This case represents an unusual presentation of M. intracellulare in a novel species.

Exposure of Threatened Accipitridae to Mycobacterium bovis Calls for Active Surveillance

Anthropogenic activities have cumulatively led to the dramatic decline of world populations of vultures that currently face serious survival challenges in several regions of the world. In Portugal, the three resident species qualify as endangered and are under conservation efforts, mainly in the central east and south-east regions, where habitat protection and artificial feeding stations were implemented. Concurrently, the areas under protection are highly affected by tuberculosis (TB) in cattle and wild ungulates, whose potentially infected carcasses may naturally or artificially be used as feed by local vultures. In this work, we opportunistically surveyed populations of Eurasian griffon (Gyps fulvus) and Eurasian black vulture (Aegypius monachus) for the presence of Mycobacterium bovis. Nine pathogenic mycobacteria, including one M. bovis isolate, were cultured from the oropharynx of nine of the surveyed vultures (n = 55), sampled in recovery centres or in artificial feeding stations. Genotyping of the M. bovis strain indicated spoligotype SB0121, the most frequent type in Portugal, and a unique MIRU-VNTR profile that differed in two loci from the profiles of SB0121 bovine and deer strains from the same geographical area. The M. bovis-positive griffon exhibited poor clinical condition when admitted to the recovery centre; however, clinical evidence of TB was not present. Although the significance of M. bovis isolation in this vulture specimen could not be ascertained and despite the accepted notion that vultures are naturally resistant to microbial pathogens, the sanitary follow-up of Accipitridae vulture populations in TB-hotspot areas is essential to safeguard ongoing conservation efforts and also to evaluate the suitability of standing legislation on deliberate supplementary feeding schemes for menaced birds of prey.

Complete Genome Sequences of Mycobacterium kansasii Strains Isolated from Rhesus Macaques

Mycobacterium kansasii is a nontuberculous mycobacterium. It causes opportunistic infections with pulmonary and extrapulmonary manifestations. We report here the complete genome sequences of two M. kansasii strains isolated from rhesus macaques. We performed genome comparisons with human and environmental isolates of M. kansasii to assess the genomic diversity of this species.

Applying the One Health Concept to Mycobacterial Research - Overcoming Parochialism

Mycobacterial infections remain a public health problem. Historically important, globally ubiquitous and with a wide host range, we are still struggling to control mycobacterial infections in humans and animals. While previous reviews have focused on individual mycobacterial infections in either humans or animals, a comprehensive review of the zoonotic aspect of mycobacteria in the context of the One Health initiative is lacking. With the purpose of providing a concise and comprehensive resource, we have collated literature to address the zoonotic potential of different mycobacterial species and elaborate on the necessity for an inter-sectorial approach to attain a new vision to combat mycobacterial infections.

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.

Wildlife health investigations: needs, challenges and recommendations

In a fast changing world with growing concerns about biodiversity loss and an increasing number of animal and human diseases emerging from wildlife, the need for effective wildlife health investigations including both surveillance and research is now widely recognized. However, procedures applicable to and knowledge acquired from studies related to domestic animal and human health can be on partly extrapolated to wildlife. This article identifies requirements and challenges inherent in wildlife health investigations, reviews important definitions and novel health investigation methods, and proposes tools and strategies for effective wildlife health surveillance programs. Impediments to wildlife health investigations are largely related to zoological, behavioral and ecological characteristics of wildlife populations and to limited access to investigation materials. These concerns should not be viewed as insurmountable but it is imperative that they are considered in study design, data analysis and result interpretation. It is particularly crucial to remember that health surveillance does not begin in the laboratory but in the fields. In this context, participatory approaches and mutual respect are essential. Furthermore, interdisciplinarity and open minds are necessary because a wide range of tools and knowledge from different fields need to be integrated in wildlife health surveillance and research. The identification of factors contributing to disease emergence requires the comparison of health and ecological data over time and among geographical regions. Finally, there is a need for the development and validation of diagnostic tests for wildlife species and for data on free-ranging population densities. Training of health professionals in wildlife diseases should also be improved. Overall, the article particularly emphasizes five needs of wildlife health investigations: communication and collaboration; use of synergies and triangulation approaches; investments for the long term; systematic collection of metadata; and harmonization of definitions and methods.

Facts and dilemmas in diagnosis of tuberculosis in wildlife

Mycobacterium bovis, causing bovine tuberculosis (BTB), has been recognized as a global threat at the wildlife-livestock-human interface, a clear "One Health" issue. Several wildlife species have been identified as maintenance hosts. Spillover of infection from these species to livestock or other wildlife species may have economic and conservation implications and infection of humans causes public health concerns, especially in developing countries. Most BTB management strategies rely on BTB testing, which can be performed for a range of purposes, from disease surveillance to diagnosing individual infected animals. New diagnostic assays are being developed for selected wildlife species. This review investigates the most frequent objectives and associated requirements for testing wildlife for tuberculosis at the level of individual animals as well as small and large populations. By aligning those with the available (immunological) ante mortem diagnostic assays, the practical challenges and limitations wildlife managers and researchers are currently faced with are highlighted.