Screening of banded mongooses (Mungos mungo) for mycobacterial infection in the Kruger National Park, South Africa

Abstract

Bovine tuberculosis (bTB) was first diagnosed in the Kruger National Park (KNP) in 1990 and research has since focused primarily on the buffalo (Syncerus caffer) as the maintenance host and lion (Panthera leo) as a clinically affected species. However, little is known about the role that small predators might play in the tuberculosis epidemiology. The aim of this pilot study was to screen banded mongoose populations in the bTB high prevalence zone of the KNP for mycobacteria in general and for Mycobacterium bovis and other Mycobacterium tuberculosis complex members in particular to detect presence of infection. Faecal swabs, tracheal swabs and tracheal lavage of 76 banded mongooses caught in cage traps within a two kilometre radius of Skukuza Rest Camp in the KNP were submitted for culture, isolation and speciation of Mycobacterium as the gold standard of bTB diagnosis. Blood was collected and serologically analysed for M. bovis and Mycobacterium tuberculosis antibodies using the ElephantTB STAT-PAK® Assay (STAT-PAK) and the EnferplexTM TB Assay (Enferplex). DPP® VetTB Assay for elephants (DPP) was used on STAT-PAK positive samples. To complement the sample set obtained from live banded mongooses 12 animals were necropsied. Lesions and pooled lymph node samples together with a standard set of organ samples were submitted for culture and histopathology analysis. Two banded mongooses had developed well demarcated, irregularly margined, greyyellow nodules of up to 5 mm diameter located in the caudal lung lobes and/ or tracheo-bronchial, retropharyngeal or superficial cervical lymph nodes. These lesions were characterised by central necrosis in the one and calcification in the other animal. Histopathologically the lesions were described as caseating necrosis associated with epithelioid macrophages and necrogranuloma with calcified centre respectively. No acid fast bacteria were identified with Ziehl-Neelsen stain. M. bovis was isolated from lung, lymph node and liver samples as well as tracheal lavages and tracheal swab from the same two banded mongooses but not from any other study animal. No other Mycobacterium of the M. tuberculosis complex was isolated. However, a variety of environmental mycobacteria, the most frequent from the Mycobacterium avium complex, M. fortuitum group, M. simiae group and M. terrae group, were cultured. M. fortuitum group was only and M. terrae group predominantly isolated from tracheal and faecal samples whereas M. simiae group and M. avium complex were the most frequent species isolated from post mortem samples, including tissue lesions and lymph nodes. Serological analysis revealed 12 banded mongooses with a positive STAT-PAK result, confirmed with DPP. Enferplex was positive for MPB83 in four and MPB70 peptide in one animal. Only two banded mongooses, the ones with the strongest positive reaction on both STAT-PAK and DPP, reacted positively on all three serological assays. These were the same two animals that had developed granulomatous lesions and that M. bovis was cultured from ante and post mortem samples. In conclusion, this study has provided the first evidence of bTB infection in banded mongooses in the KNP and demonstrated their ability to shed M. bovis. This finding has opened the discussion around possible sources of infection and its significance at the human/ wildlife interface in and around Skukuza.