Viability of Mycobacterium Bovis in traditionally processed Sour Milk and the prevalence of Bovine Tuberculosis in Namwala district of Zambia
Date
2012-09-17
Authors
Sitima, Almond Casmir Madandu
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Abstract
Tuberculosis is a debilitating disease caused by the bacteria of the genus Mycobacterium. The disease has been recognized for centuries and its causative agents have continued to be studied to date. Mycobacterium species cause disease in animals, birds and humans. They can cause cross infection between the hosts. The most important species in the genus are Mycobacterium bovis and Mycobacterium tuberculosis. These two cause zoonotic tuberculosis and can be excreted in milk of co.ws when udders are infected making the milk to be a very good vehicle for mycobacterium transmission.Several authors have indicated that tuberculosis is transmitted by consuming contaminated milk. The Ila people of Namwala district in Zambia are cattle keepers and consume a lot of milk both as fresh and sour. MilkJs allowed to sour in a bottle gourd {Lagenaria siceraria) commonly known as a calabash {Insuwa-lla. and Tonga, A^5Mpa-Chewa, Insupa-Qtrabo). The Ila people boil milk for immediate use but that meant for sour milk remains unboiled. The prevalence of bovine tuberculosis has been reported to be as high as 30 percent in their herds of cattle based on assumptions and abattoir returns. The risk of humans to be infected with mycobacterium may be seen to be high.
Therefore aims of the study were; to assess the viability of M. bovis in traditionally processed milk, to estimate the prevalence of bovine tuberculosis in cattle of Namwala district and to identify the flora in the calabash.Within Namwala district data was collected from Baambwe and Maala Villages due to proximity and high cattle populations. Tuberculin test was used to estimate the prevalence of bovine tuberculosis. The tuberculin used was Purified Protein Derivative of Mycobacterium bovis and Mycobacterium avium manufactured in the Netherlands. Ten herds of cattle, totaling 507 cattle were tested. To assess the effect of traditional milk processing on M. bovis, a laboratory experiment was set to imitate the traditional method of souring milk. M. bovis was inoculated into fresh milk which was mixed with a cocktail of souf milk collected from calabashes . Samples of this milk were taken at intervals to measure the pH and for culturing on Lowenstein-Jensen medium, to determine the viability of the M. bovis and M tuberculosis . Samples of sour milk were taken from 14 calabashes for the identification of the flora in the calabashes. M. bovis was recovered at the various stages of the pH transition from 7.0 to 3.0 and at all sampling intervals from the milk in which it was inoculated experimentally. The obtained results indicate that raw milk containing M. bovis is not able to eliminate the organism in the process of souring the milk within the time frame of optimal consumption (24-48 hours).The overall prevalence of bovine tuberculosis was found to be 12.8 percent. In the females it was found to be 13.5 percent while in the males 8.6 percent. It was highest, (17.6 %), in the age group of 41-55 months old while the youngest 1-24 months had the lowest (6.3 %). The herd prevalence of the ten herds varied between 9.4 and 18.8 percent.The high quantity of the lipids in the cell wall of the M. bovis was thought to account for the recovery of viable Mycobacterium in sour milk. Bacteria and yeast found to form the flora of the calabashes were mostly the Gram positive rods of the lactobacillus species and Candida species respectively.
It was concluded from the present study that the prevalence of bovine tuberculosis in Namwala district was high as compared to other districts in the country and that the traditional way of sour milk processing' presents a public health risk.
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Keywords
Tuberculosis in Cattle -- Zambia , Mycobacterium bovis -- Zambia