INTRODUCTION
Bovine tuberculosis (bTB) is a chronic disease, caused primarily byM. bovis , affecting cattle, other domesticated animals, certain wildlife species, non-human primates, and humans.1-3Cattle can be infected at any age, but tubercle lesion development and subsequent clinical signs may appear at a later stages. Calves can be born with tuberculosis congenitally when infected with M. boviseither via the umbilical vein from an infected genital tract of the dam, from the infected placenta, or from infected amniotic fluid.4 After birth, neonates can also be infected even at an early stages following delivery, mainly by inhaling infected droplets and/ or by ingesting raw milk or colostrum from infected cows. Other routes of infection such as cutaneous, though not common, are still important in situations where the prevalence of bTB is high.5 As the course of the disease is slow compared to many other infectious diseases, infected animals can spread bTB to other herd mates and newborns before it begins to manifest clinical signs. The transmission rate may be faster at late stages of infection as the number of organisms being shed is larger in this stage.1
The observation of characteristic tubercle lesions in the lungs of a three weeks old male calf led us to raise questions like ‘how the calf could get the infection?’ and ‘how fast is the disease progression under natural infection?’. In order to get answers to these questions, further investigation was made and this case report was compiled from the pathological and molecular investigations conducted for the diagnosis of the case.