Cross sectional study of bovine and avian tuberculosis in Bangladesh Livestock Reasearch Institute ( BLRI ) cattle farm

The present study was carried out to determine the prevalence of bovine and avian tuberculosis in cattle by using bovine and avian PPDs at Bangladesh Livestock Research Institute (BLRI) Cattle Farm, Savar, Dhaka. Cattle of different breeds, ages and sexes (n=183) were tested using bovine and avian PPDs. In caudal Fold Tuberculin (CFT) test, 16 (8.74%) cases were showed positive reaction among 183 sample. The overall percentages of positive reactors to Comparative cervical tuberculin (CCT) test of bovine and avian tuberculosis were 7.10% and 1.64% respectively. An insignificant variation (P>0.05) on prevalence of bovine tuberculosis on different age group of cattle was observed. Age group >7 years showed a higher prevalence (10.91%) than those of other age groups. In CCT test, 7.55% and 4.17% positive reactors were found in female and male cattle respectively. The association between different breeds of the animal was found significant (P<0.05). The local breed showed higher prevalence (9.77%) than those of Red Chittagong and cross breed. The highest percentage (10.45%) of positive reactors in CCT test was recorded in milking cows than in dry cows (2.32%), heifer (9.52%) and calf (5.77%) were observed. Mixed infection (bovine and avian type of tuberculosis) was recorded 1.64%.


Introduction
Bovine tuberculosis is one of the most important zoonotic diseases (Thoen et al., 2006) of cattle and other farm animals, known to exist in all part of the world.It is an infectious disease caused by Mycobacterium bovis that has a broad host range (Wedlock et al., 2002).Bovine tuberculosis was responsible for approximately 6% of total human tuberculosis deaths in 1930-1940(Vordermeier et al., 2001)).Mycobacterium bovis can be transmitted from cattle to human, human to human and from human to cattle (Griffith and Munro, 1944).Thus, it is a great concern to determine the prevalence of bovine tuberculosis in Bangladesh.The several countries or farms does this survey regularly.The most popular, easy and cheap technique for detection of tuberculosis is tuberculin test (Ameni and Erkihun, 2007;Fikru et al., 2005).The prevalence is 6.8% in Zambia (Munyeme et al., 2009), 7.3% in Pakistan (Aranaz et al., 1996), 10% in Kenya (Kang'ethe et al., 2007), 19% in Ethiopia (Laval and Ameni, 2004), 26.4% in Eritrea (Omer et al., 2001) and 13.2% in Tanzania (Kazwala et al., 2001).
Bovine tuberculosis is economically important for cattle farming and very few studies were conducted in cattle in Bangladesh as yet.The use of tuberculin test among cattle, of Mymensingh and Pabna districts showed 1.22% (Yakub, 1974), which indicated the prevalence of this infection in animals of Bangladesh.Samad and Rahman (1986), at Bangladesh Agricultural University Dairy Farm (BAUDF) conducted tuberculin test in cattle to detect the incidence of bovine tuberculosis in unorganized and organized farms of Bangladesh revealed 3.05% overall incidence of tuberculosis.That's why the need was strongly felt to have a new data about the situation of tuberculosis in cattle on the basis of tuberculin testing at Bangladesh Livestock Research Institute (BLRI).The main objectives of this study areto find out the prevalence of bovine tuberculosis in cattle in Bangladesh Livestock Research Institute (BLRI), to compare the prevalence of tuberculosis among the different breeds of cattleand to compare the prevalence of tuberculosis in different age, types and sex groups of cattle.

Materials and Methods
The whole study was conducted in the Bangladesh Livestock Research Institute (BLRI) Cattle Farm, Savar, Dhaka during the period from January to June, 2010 to determine the prevalence of bovine and avian tuberculosis.Total 183 cattle were divided into several groups on the basis of age, breed, sex and types of animals.Out of the 183, 44 cattle were Red Chittagong (RCC), 133 were Local (Pabna) and 6 were Cross breed cattle.159 cattle were female and 24 nos.were male cattle.Date of birth and other necessary information were recorded in a questionnaire from the register book of the farm.Cattle were tested by Caudal Fold Tuberculin Test (CFT) which is a single Intradermal tuberculin test using bovine Purified Protein Derivatives (bPPD) at the caudal fold.Among the 183 Cattle, the positive responders were further subjected to Comparative Cervical Tuberculin Test (CCT) using both bovine (bPPD) and avian Purified Protein Derivatives (aPPD).The results were recorded in questionnaire and finally analyzed to determine the prevalence and risk factors associated with the prevalence of tuberculosis in cattle.The bPPD was given two times in each and every cattle (primary and cofirmatory test).The first dose was given with an equivalent dosage of 10,000 tuberculin unit/ml at caudal fold and after a period of 10 days the comparative intradermal inoculation was made by 10,000 tuberculin unit/ml of bovine type PPD and 2,500 tuberculin unit /ml of avian type PPD in separate way on one side (upper and lower) of the neck region.Method described by Welchi, (1915) was followed throughout the experiment for inoculating the animals.Reading was taken for one times after 72 hours (± 6 hours) after the inoculation of PPD.The positive tuberculin reaction was evident from an inflammation of sensitive nature at the point of inoculation.The area of the characteristic swelling ranged from the size of a small pea to that of an orange.The reaction sites indicated the organism responsible for the sensitization.The swelling was either soft and edematous or somewhat hard in nature.The swelling was estimated by palpation at the site of inoculation, while the animal showed the sign of pain.In Comparative Cervical Tuberculin (CCT) test two injections were made intradermally; bPPD at upper site and aPPD at lower site at neck region.Initial skin thickness was measured before inoculation PPD.Reading was taken after 72(±6) hours with slide calipers.The difference of skin thickness was measured and recorded.The data collected by questionare and was analyzed in MS excel and SPSS.

Result
Out of 183 cattle, 16 cattle positively responded with a percentage of 8.74% to CFT test with bovine type tuberculin (Table 1).Comparative Cervical Tuberculin (CCT) test which revealed that the overall percentage of reactors were 7.10% and 1.64% with bovine type of PPD and avian type of PPD respectively and doubtful cases were 1.09% and 0.54% with bovine and avian type of PPD respectively (Table 2).Out of the 183 cattle which were subjected to Comparative cervical tuberculin (CCT) test, the number of male reactor was 1 having a percentage of 4.17% while the numbers of female reactors were 12 having a percentage of 7.55% (Table 3).Among the 183 cattle of different breeds, the overall percentages of reactors were 0.00%, 9.77%, 0.00% for the Red Chittagong, Local (Pabna) and Cross breed respectively (Table 5).The highest percentages (10.45%) of positive reactors in Comparative cervical tuberculin (CCT) test were found in milking cows.The percentages of positive reactors in dry cows, heifer and calves were recorded 2.32%, 9.52% and 5.77% respectively (Table 6)., 2007, Ameni and Erkihun, 2007, Omer et al., 2001and Kazwala et al., 2001 who found 10%, 11%, 14.5% and 13.2% positive reactors respectively by CCT test.On the other hand, positive reactors (7.10%) obtained in this study were higher than those obtained by Laval and Ameni, 2004, Fikru et al., 2005and Solmaz et al., 2009 who reported 4.1%, 3.4% and 1.42% bovine TB respectively.In CCT test, 7.55% and 4.17% positive reactors were found in female and male cattle respectively.No significant relation was found (P>0.05) between tuberculosis and sex of the animal.However, the male cattle showed relatively low incidence than female cattle in this study.It may be due to the fact that male cattle are reared in individual pen and grazing is not practiced so there is a low chance of infection which may be one of the reasons of low prevalence of bovine tuberculosis in male cattle.In this study, 9.77% of bovine TB reactors by CCT test were found in local (Pabna) breed.However, no positive reactors were found in Red Chittagong and Cross breed cattle.The association between different breeds of the animal was found significant (P<0.05).This result revealed that Red Chittagong (RCC) has greater resistance than that of local (Pabna) breed.Although cross breed exhibited no reactors which might be due to the fact that a very few cross breed (n=6) animals have been tested.In case of RCC, it may be concluded that the body structure of RCC are strong and stout and more resistance to all types diseases, which may be one of the reasons of low prevalence of bovine tuberculosis in RCC.
The present study showed a non-significant variation (P>0.05) on prevalence of bovine tuberculosis on different age group of cattle.Age group >7 years showed a higher prevalence (10.91%) than those of other age groups.It may be stated that cattle of ages more than 7 years are most prone to the infection due to decrease of immune status because of their old age and low resistance to tuberculosis infections and malnutrition.However, the younger and older animals of the study area were found more infected with tuberculosis than the animals of middle age.The greater incidence in younger animals was in accord with the results of Rashid et al., 1970 andLubrini, 1963.No significant relation was found (P>0.05) between tuberculosis and the types of animal.Milking cows showed relatively high positive reactors than those of dry cow, heifer and calves.It may be concluded that during lactation period animals remain in stress condition and this may be one of the reasons for higher prevalence in milking cows.Mixed infection (bovine and avian type of tuberculosis) 1.64% was observed in the study area (Table 2).It may be due to close contact with the various indigenous and migratory birds present in the lakes of BLRI campus.It may not represent the actual incidence of Bovine Tuberculosis in this country.Because, the rate of incidence of bovine tuberculosis is influenced by many factors such as geographical situation of a country, and weather, hygienic status of men and animals, and control measure taken by Public Health and Veterinary Public Health sector.

Conclusions
This study was undertaken to determine the prevalence of bovine and avian tuberculosis in Bangladesh Livestock Research Institute (BLRI), Savar, Dhaka.In the Caudal Fold Tuberculin (CFT) test the percentage of positive responder was found to be 8.74.In the Comparative Cervical Tuberculin (CCT) test the percentage of positive reactors were 7.10 and 1.64 to the test with bovine PPD and avian PPD respectively.Mixed infection was recorded in 1.64% cattle.The cross breeds showed minimum (0.00%) and the local (Pabna) breed showed maximum (9.77%) percentage of positive reactors.The Red Chittagong (RCC) breed also exhibited 0.00% of positive reactors in the Comparative Cervical Tuberculin (CCT) test.In general the female, the younger and the older animals were found to be higher positive reactors than the male and adult animals in this study.In comparison with relevant literature that in general the percentage of reactors to tuberculin was low in this study in comparison with those of other parts of the world.

Table 6 . The overall Comparative cervical tuberculin (CCT) test with bovine type of PPD on the basis of type of animal.
Munyeme et al., 2009 andAranaz et al., 1996T test are in close agreement with the findings ofMunyeme et al., 2009 andAranaz et al., 1996who found 6.8% and 7.3% bovine TB positive cases respectively by CCT test.The percentages of reactors to tuberculin tests in cattle were found almost moderate in this study.In our study positive reactors (7.10%) were much lower than that reported by Kang'e the et al.