Zoonotic tuberculosis in a high bovine tuberculosis burden area of Ethiopia

Background

Tuberculosis (TB) is a major cause of ill health and one of the leading causes of death worldwide, caused by species of the Mycobacterium tuberculosis complex (MTBC), with Mycobacterium tuberculosis being the dominant pathogen in humans and Mycobacterium bovis in cattle. Zoonotic transmission of TB (zTB) to humans is frequent particularly where TB prevalence is high in cattle. In this study, we explored the prevalence of zTB in central Ethiopia, an area highly affected by bovine TB (bTB) in cattle.

Method

A convenient sample of 385 patients with pulmonary tuberculosis (PTB, N = 287) and tuberculous lymphadenitis (TBLN, N = 98) were included in this cross-sectional study in central Ethiopia. Sputum and fine needle aspirate (FNA) samples were obtained from patients with PTB and TBLN, respectively, and cultures were performed using BACTEC™ MGIT™ 960. All culture positive samples were subjected to quantitative PCR (qPCR) assays, targeting IS1081, RD9 and RD4 genomic regions for detection of MTBC, M. tuberculosis and M. bovis, respectively.

Results

Two hundred and fifty-five out of 385 sampled patients were culture positive and all were isolates identified as MTBC by being positive for the IS1081 assay. Among them, 249 (97.6%) samples had also a positive RD9 result (intact RD9 locus) and were consequently classified as M. tuberculosis. The remaining six (2.4%) isolates were RD4 deficient and thereby classified as M. bovis. Five out of these six M. bovis strains originated from PTB patients whereas one was isolated from a TBLN patient. Occupational risk and the widespread consumption of raw animal products were identified as potential sources of M. bovis infection in humans, and the isolation of M. bovis from PTB patients suggests the possibility of human-to-human transmission, particularly in patients with no known contact history with animals.

Conclusion

The detected proportion of culture positive cases of 2.4% being M. bovis from this region was higher zTB rate than previously reported for the general population of Ethiopia. Patients with M. bovis infection are more likely to get less efficient TB treatment because M. bovis is inherently resistant to pyrazinamide. MTBC species identification should be performed where M. bovis is common in cattle, especially in patients who have a history of recurrence or treatment failure.

Impact of sawdust and wood shavings in bedding on pig tuberculous lesions in lymph nodes, and IS1245 RFLP analysis of Mycobacterium avium subsp. hominissuis of serotypes 6 and 8 isolated from pigs and environment

Among 25,027 slaughter pigs raised in two farms, tuberculous lesions were detected in the lymph nodes of 898 (3.6%) of them. Tuberculous lesions were most commonly found in the mesenteric (601; 2.4%) and head (451; 1.8%) lymph nodes. Mycobacteria were isolated from 49 of 120 randomly selected mesenteric, head and bronchial lymph nodes with diagnosed tuberculosis originating from both farms. Forty six Mycobacterium avium subsp. hominissuis, one M. chelonae and two M. fortuitum isolates were found in the lymph nodes of pigs. No statistically significant difference was detected between farms A and B for isolation rates of mycobacteria from the lymph nodes of pigs and their species composition. To investigate the source of the pigs' infections, culture examinations of 117 samples from the external environment were performed. Mycobacteria were isolated from 25 samples from the external environment (21.4%). Mycobacterial isolates were also detected in eleven (91.7%) and two (16.7%) of 12 used sawdust and 12 of non-used (fresh) sawdust samples, respectively. None of 12 wood shavings was culture-positive. Twelve of 13 sawdust isolates were classified as M. a. hominissuis of serotypes 6 and 8 and genotype IS901- and IS1245+; the remaining isolate was classified as species M. fortuitum. Other conditionally pathogenic mycobacteria were only isolated from 12 of the remaining 81 samples from the external environment (excluding bedding). A total of eight isolates (two pig and six sawdust samples originating from farms A and B) were examined by IS1245 restriction fragment length polymorphism (IS1245 RFLP) analysis. These isolates produced five distinct IS1245 RFLP types with more than 20 bands. Based on identical IS1245 RFLP types of one pig isolate and two isolates of used sawdust from farm A, we have concluded that contaminated sawdust was the source of mycobacterial infection for pigs in our study.

Milk containing Mycobacterium bovis as a source of infection for white-tailed deer fawns (Odocoileus virginianus)

SETTING

White-tailed deer represent the first wildlife reservoir of Mycobacterium bovis in the United States. The behavior of does with nursing fawns provides several potential mechanisms for disease transmission. Little information exists concerning transmission between doe and fawn, specifically transmammary transmission.

OBJECTIVE

Determine if fawns can become infected by ingestion of milk replacer containing M. bovis, thus simulating transmission from doe to fawn through contaminated milk.

DESIGN

Seventeen, 21-day-old white-tailed deer fawns were inoculated orally with 2 x 10(8) CFU (high dose, n=5), 2.5 x 10(5) to 2.5 x 10(6) CFU (medium dose, n=5), and 1 x 10(4) CFU (low dose, n=5) of M. bovis in milk replacer. Dosages were divided equally and fed daily over a 5-day period. Positive control fawns (n=2) received 1 x 10(5) CFU of M. bovis instilled in the tonsillar crypts. Fawns were euthanized and examined 35-115 days after inoculation and various tissues collected for bacteriologic and microscopic analysis.

RESULTS

All fawns in the tonsillar, high oral and medium oral dose groups developed generalized tuberculosis involving numerous organs and tissues by 35-84 days after inoculation. Three of five fawns in the low-dose oral group had tuberculous lesions in the mandibular lymph node, and one of five had lesions in the medial retropharyngeal lymph node when examined 115 days after inoculation.

CONCLUSION

White-tailed deer fawns can become infected through oral exposure to M. bovis. Therefore, the potential exists for fawns to acquire M. bovis while nursing tuberculous does.

Tuberculosis in kudus (Tragelaphus strepsiceros) in the Kruger National Park

Five kudus (Tragelaphus strepsiceros), three bulls and two cows, within the Greater Kruger National Park complex, were diagnosed with generalized tuberculosis caused by Mycobacterium bovis. The lesions seen in these animals were similar to those previously reported in kudus and included severe tuberculous lymphadenitis of the nodes of the head and neck (that resulted in noticeable uni- or bilateral swelling beneath the ear), thorax, and the mesentery. All the animals also suffered from severe granulomatous pneumonia. The lesions in the lungs were more severe cranially and had a miliary distribution elsewhere in the lungs. Based on the DNA patterns of the M. bovis isolates, at least some of these kudus were infected with strains commonly present in tuberculous buffaloes, lions, cheetahs, and baboons in the Park whereas other strains from these kudus were quite different and may reflect another source of infection. The presence of tuberculous kudus in the Park is expected to complicate control measures that may be instituted to contain or eradicate the disease in the Park.

Tuberculosis, caused by Mycobacterium bovis, in a kudu (Tragelaphus strepsiceros) from a commercial game farm in the Malelane area of the Mpumalanga Province, South Africa

Tuberculosis, caused by Mycobacterium bovis, was diagnosed for the first time, in a kudu cow from a commercial game ranch in the Malelane area of the Mpumalanga Province close to the Kruger National Park. This diagnosis has important implications for the eradication of the disease in commercial and communal livestock in the area. Kudus are considered to be a potential maintenance host and, because of discharging fistulae in the parotid area where the lymph nodes are commonly infected, they have the potential of disseminating bacteria over wide areas. Cognisance should be taken of the presence of tuberculosis in a species other than domesticated cattle in this area and its implications for the control of tuberculosis in cattle.

[Tuberculosis lymphadenitis in slaughtered swine from the State of São Paulo, Brazil: microscopic histopathology and demonstration of mycobacteria]

INTRODUCTION

As the occurrence of tuberculosis lymphadenitis in swine constitutes a public health risk, especially in immunosuppressed individuals, the distribution of tuberculoid lesions and the presence of microbacteria in lymph nodes and hepatic and muscular tissue in swine for slaughter, in the State of S. Paulo, SP (Brazil), in the period from 1993 to 1994, were studied. MATERIAL E METHOD: Tuberculous lesions in 60 carcasses of swine, slaughtered at abattoirs during the period 1993-1994, were studied. When macroscopic lesions were observed, a representative sampling of lymph nodes, hepatic and muscular tissues (masseter and diaphragm) were examined using histopathological and microbacterial isolation techniques.

RESULTS

The macroscopic lesions were found predominantly in mesenteric lymph nodes. The MAI Complex (M.avium-intracellulare) was isolated mainly in the carcass group that showed lesions and was not found in the control group. Microorganisms of the MAI Complex were not isolated from hepatic and muscular tissues.

CONCLUSION

No clear relationship between the type of mycobacteria isolated and the macroscopic lesions observed during the carcass inspection was found.

An abattoir study of tuberculosis in a herd of farmed elk

The purpose of this study was to examine the prevalence and distribution of grossly visible lesions of tuberculosis in a herd of 344 North American elk (Cervus elaphus) depopulated during a three-month period in 1991. Abattoir inspection detected mycobacterial lesions in 134 (39.8%) of the 337 animals received for slaughter. The prevalence of lesions increased with the age of the animals. Lesions were predominantly suppurative rather than caseous, and mineralization was less evident than in tuberculous lesions in cattle. Lesions occurred predominantly in lymph nodes, and lungs were the only organs in which mycobacterial lesions were found. The distribution of lesions suggested that aerosol transmission was the most significant means of spread of the disease within the herd. Giant liver flukes (Fascioloides magna) were observed in approximately 80% of the adult elk.

[Pilot study for radiometric detection of mycobacteria in lymph nodes altered by tuberculosis in slaughtered animals]

30 lymph nodes with tuberculous changes from slaughter animals were investigated, comparing radiometric and usual cultural methods for presence of mycobacteria. Mycobacteria were isolated with help of radiometric method (BACTEC 460-TB) from 24 lymph nodes ("sensitivity" 96%, "specificity" 83.3%), and with help of usual cultural method from 22 lymph nodes ("sensitivity" 88%, "specificity" 62.5%). The radiometric method is suitable for isolating of mycobacteria in veterinary medicine diagnostic also.

Tuberculosis in domesticated deer (Cervus elaphus): a large animal model for human tuberculosis

Since the recent extensive domestication and farming of deer in New Zealand, tuberculosis (Tb) has presented a major health issue in farmed herds. The spectrum of disease pathology and immune reactivity in this naturally infected species represents a potentially valuable large animal model for the study of the underlying immunological and pathological mechanisms involved in Mycobacterium bovis infection and its spread. A combination of laboratory assays for the detection of tuberculosis in deer is described. Domesticated deer are genetically diverse and their exposure to natural variations in environmental conditions results in a spectrum of immune responses and pathology of Tb, similar to that found in man. The model has special relevance to the study of host responses to tuberculosis in immunocompromised individuals, particularly those in the third world. Elucidation of the mechanisms involved in immune responses to Tb in deer will facilitate the development of vaccines and improved diagnostic assays for Tb in man.

Mycobacterium avium infection through the alimentary tract in mice

Intestinal infection by Mycobacterium avium was investigated in C57BL/6 and BALB/c mouse strains. Single intragastric administration of a massive dose (10(8] or multiple administration of a lower dose (10(7), 10 times) established infection principally in the mesenteric lymph-node (MLN); a continuous or intermittent fecal excretion of the bacilli was detected by 6-8 weeks after the administration. Based on three criteria--isolation of the organisms from the MLN and from feces, and detection of acid-fast bacilli in sections of the MLN--germ-free (GF) BALB/c mice exhibited clearer dose-effect relations than the flora-bearing (FB) counterparts. After intragastric administration, the organisms were probably trapped in the Peyer's patch and then transferred to the MLN at an early period (by 4-7 days), persistent infection thus being established in the MLN. Systemic involvement evolved both in athymic and euthymic mice after a prolonged period of time (more than 40 weeks) showing far more severe involvement in the former regardless of the presence of floral organisms.

Tuberculosis in five basset hounds

Five Basset Hounds (2 females and 3 males) under the age of 5 years, acquired systemic tuberculosis. We suspected tuberculosis in one dog, because it had histologic lesions similar to those in 4 dogs in which bacteria were identified as Mycobacterium avium complex. A review of canine tuberculosis revealed a similar diagnosis in a Basset Hound. The association of this infection in Basset Hounds suggests an inherited immunologic defect. Results of our survey suggest that the defect might exist in cell-mediated immunity.

Mycobacterium bovis in the anterior respiratory tracts in the heads of tuberculin-reacting cattle

Twenty-five of 50 randomly selected tuberculin-reacting cattle were confirmed as tuberculous in the laboratory. All 25 cattle had macroscopic lesions in lymph nodes associated with the respiratory tracts but only one had lung lesions. M bovis was isolated from the anterior respiratory tracts in the heads of four of the 25 tuberculous animals and from a nostril lesion found in a fifth. For at least three of these five animals, the intervals between the final tuberculin test and their previously negative tests indicated that infection had established relatively rapidly. Four of them had been tuberculin tested solely because they were animals in contiguous 'at risk' herds. It would appear that although M bovis can be isolated from the anterior respiratory tracts in the heads of tuberculin-reacting cattle, it is unlikely that primary foci of infection exist in regions other than the lungs or associated tissues. The study demonstrates the potential for reactors with lesions to excrete M bovis and the continued importance of infected cattle in the epidemiology and eradication of the disease.

[Pseudotuberculosis in goats also in the Netherlands. A literature review]

Pseudotuberculosis or caseous lymphadenitis in goats is marked by superficial abscesses and was recently observed in the Netherlands. The literature on this disease is reviewed, concerning the incidence, aetiology, pathogenesis, symptoms, diagnosis, therapy and preventive measures. The damage which the disease could cause to goat husbandry in the Netherlands, is discussed. Although the losses from death and diminished production will probably be small, treatment is time-consuming and requires much labour. The greatest damage will possibly consist in the fact that breeders will not be able to sell their animals when caseous lymphadenitis occurs in their herd. Particularly, the export of breeding stock could be menaced by this disease.

Isolation of Mycobacterium kansasii from lymph nodes of cattle in the United States

The isolation of 6 strains of Mycobacterium kansasii from bovine lymph nodes is reported. Occasional isolations of this organism from cattle lymph node lesions provides further evidence of its pathogenicity in domestic animals. The isolates were similar as determined by biochemical and serologic examinations. Histopathologic changes induced by this organism relative to those by M bovis and factors regarding source of infection are discussed.

[Modification of the koch bacillus by a material extracted from tuberculosis lesions]

Lymph node lesions of tuberculous cattle and swine gave, after disruption, centrifugation through 2.2 M sucrose, and ultrafiltration, a material that brings about, in vitro, modification of the tubercle bacilli or chromogenic mycobacteria into bacterial elements that are not acid fast, rapidly growing on nutritive agar supplemented with glycerol. The phenomenon is similar to that which the authors have previously described, using an inducing agent extracted from cultures of mycobacteria, called "endometallaxic conversion."

Epidemiology of mycobacterial lymphadenitis in an Idaho swine herd

A study of Mycobacterium avium infected swine in an Idaho herd was made to obtain information on morbidity and to evaluate some control measures. Of 867 pigs slaughtered during a 30-day period in May and June, 1974, 100 carcasses were condemned or passed for cooking and 406 carcasses had lesions in one lymph node and were passed without restriction. Mycobacteriologic examinations were made on 33 pigs which were tuberculin tested. Mycobacterium avium was isolated from 21 of 26 tuberculin positive pigs and from 4 to 7 tuberculin negative pigs. Lymphocyte stimulation tests were completed for 12 pigs. Positive results were observed in 11 and M. avium was isolated from 7. Mycobacterium avium serotypes 1,2,4,8, and 9 were identified.

Tuberculosis in brood sows and pigs slaughtered in Iowa

Mycobacterium avium was isolated from 21 of 23 lymph nodes with lesions collected from 23 brood sows and from 17 lymph nodes with lesions of 17 pigs slaughtered at an abattoir in north central Iowa. Mycobacterium avium serotype 2 accounted for more than 65% of the isolations in sows and in pigs. Granulomas with acid-fast bacilli were found in 15 of 23 tissues from brood sows and in 13 of 17 lymph nodes from pigs. Similar microscopic lesions were observed in the sows and pigs.

Tuberculosis in wild badgers (Meles meles) in Gloucestershire: pathology

The gross and histological appearances of the lesions of tuberculosis in 36 wild badgers found to be infected with Mycobacterium bovis are described. These badgers were examined over a period of two years during an investigation into the possible epidemiological association of tuberculosis in badgers and cattle. The possible significance of the lesions in transmission of M bovis to cattle and other badgers is discussed. The histological appearance of the lesions was considered to be indicative of a lesser hypersensitivity reaction than is seen in the bovine.

Swine tuberculosis in South Dakota

Mycobacteria were isolated from 195 of 200 lesions in lymph nodes identified as granulomatous by meat inspectors at 4 abattoirs in South Dakota. Mycobacterium avium serotypes 1 and 2 accounted for 89% of the isolants. Mycobacteria were isolated more frequently from lesions than acid-fast bacilli were observed on microscopic examination (P less than 0.001). The frequency with which mycobacteria was isolated was similar to the occurrence of granulomatous lesions. The numbers of the various kinds of mycobacteria isolated at each of the 4 abattoirs and for the 3 meat inspection disposition classes were not significantly different.

Lesions and tuberculin sensitivity in calves inoculated with group III mycobacterial isolates from swine, pen soil, and cattle feed

FIFTEEN calves, 7 to 11 months of age, were inoculated intradermally with group III mycobacteria ---6 isolates from swine, 1 isolate from cattle feed, and 2 isolates from soil of swine farrowing pens. Calves were tuberculin tested at 50 days and killed approximately 60 days after inoculation. Only 1 of the cultures, that of porcine origin (93c-0), produced any lesions. There were a caseo-calcareous granuloma 3mm in diameter in the regional lymph node (left prescapular) and a granuloma at the skin inoculation site. None of the 5 calves inoculated with soil- or feed-origin mycobacteria had any lesions. Three of the calves inoculated with porcine origin group III mycobacteria had suspicious or positive caudal fold reactions. Two of these had granulomas at the skin-inoculation sites and one had no lesions. The calf having lymph node and skin-inoculation site granulomas was negative. The 5 calves inoculated with feed- or soil-origin mycobacteria had negative caudal fold tuberculin tests.

Runyon group III atypical mycobacteria as a cause of tuberculosis in a rhesus monkey

Bilateral draining fistulas which communicated with the cheek pouches were noted in the threat region of an adult femal Macaca mulatta receiving isoniazid for tuberculosis prophylaxis. Necrospy findings included enlargedregional lymph nodes and ulceration of cheek pouch mucous membranes. Acid-fast bacilli were demonstrated in tissue section. Cultures of the regional lymph nodes and cheek pouch mucous membrane yielded Runyon Group III mycobacteria. Intrapalpebral tuberculin tests with homologous mycobacterial antigen (Battery strain PPD) and Kochs Old Tuberculin were performed in an unsuccessful attempt to identify additional infected monkeys. This case is considered significant because of the unusual manifestation of mycobacterial disease and its occurrence in an animal receiving isoniazid at levels considered sufficient for the prevention of tuberculosis.