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Tuberculosis in dairy calves: risk of Mycobacterium spp. exposure associated with management of colostrum and milk
ELSEVIER
PFJEVENTNE VETERINARY MEDICINE Preventive Veterinary Medicine 27 (19%) 23-27
Tuberculosis in dairy calves: risk of M’ycobacterium spp. exposure associated with management of colostrum and milk Tom& B. Renteria Evangelista, Jorge HemGndez De Anda
*
Institute de Inuestigaciones en Ciencias Veterinarias, Unioersidad Auto’rwmade Baja California, 21100 Mexicali, BC, Mkxico
Accepted 6 October 1995
Abstract A prospective
study was undertaken to investigate the association between the risk of spp. exposure and management of colostrum and milk in two groups of Holstein calves in a Mycobucterium bouis infected commercial dairy herd in Mexico. Group 1 (high risk) included !>l calves fed with pooled colostrum from several cows in the study herd and raw milk from the bulk tank. Group 2 (low risk) was composed of 279 calves fed with colostrum from tuberculin skin-test negative cows and powdered milk. At 6 months of age, calves in Groups 1 and 2 were skin-tested for detection of Mycobacterium spp. exposure. In the high risk group, 25 (27%) of 91 calves tested positive to the caudal fold skin-test; in the low risk group, 43 (15%) of 279 calves were also classified as positive. After controlling for the confounding effect of skin-test reactor status of dams, it was found that the risk of Mycobucterium spp. exposure was associated with management of colostrum and milk. The adjusted odds for Mycobucterium spp. exposure were 1.9 times higher in the high risk group when compared with the low risk group (P = 0.05). Further, the risk of skin-test reactors increased from 11% in calves born from skin-test negative cows (in the low risk group) to 33% in calves born from skin-test positive cows (in the high risk group).
Mycobacferium
1. Introdluction Bovinie tuberculosis industry.
The disease
(TB) is an important could
cause
important
animal trade
health
issue in the Mexican
complications
* Correstlonding author at: IICV UABC, PO BOX2902, Calexico, CA 92232, USA. 0167-5877/%/$15X@ 0 1996 Elsevier Science B.V. SSDI 0165-5877(95)00573-O
livestock
for the Mexican
dairy
24
T.&R. Evangelista, J.H.D. Andu / Preventive Veterinary Medicine 27 (1996) 23-27
and beef industries. During 1981-1990, based on slaughter surveillance, United States Department of Agriculture investigations have shown that, on average, 67% of all TB cases in cattle in the USA were related to steers of Mexican origin (Essey, 1990). In 1992-1993, Mexico exported about 1300000 steers to the USA. In that period, 299 TB cases in cattle were confirmed in the USA; 210 (70%) of these TB cases were traced back to Mexico. Additionally, it was determined that 137 (65%) of those 210 cases were Holstein steers (Essey, 1993). This finding prompted animal health authorities in Mexico to prohibit the export of Holstein steers of Mexican origin to the USA. In Baja California, Mexico, the dairy cattle population is about 50000 animals kept in approximately 500 dairy farms (about half in only 50 farms). The number of milking cows in commercial dairy farms may range from 100 to 1000 and the daily average milk production per cow may range from 18 lb in the summer to 35 lb in the winter (Baja California Cattleman’s Association, 1993). Currently, strategies to prevent the spread of TB in the dairy cattle population include slaughter surveillance, skin-testing, animal movement restrictions, and, if possible, slaughter of skin-test positive animals, but an indemnity program does not yet exist. Consequently, management practices within herds, such as segregation of infected animals and management of colostrum and milk, have been implemented in some dairy herds to reduce the incidence of the disease. However, in Mexico no epidemiological studies of the relationship between the risk of TB and these management practices have been conducted. The objective of the present study was to estimate the strength of relationship between tuberculin reactor status in Holstein calves and milk feeding management in a Mycobacterium bovis infected commercial dairy herd.
2. Materials
and methods
2.1. Study design In August
1992, all cows (600) in the study herd were skin-tested for detection of spp. exposure, using the caudal fold tuberculin skin-test. Thirty percent of all tested cows were classified as skin-test reactors. Based on this result, cows were separated into ‘hot pens’ for reactor and ‘clean pens’ for non-reactor animals. In October 1992, Mycobacterium bovis was isolated from pleural lesions in a milking cow sent to slaughter. At the abattoir, the carcass was confiscated because of the presence of TB-like lesions. Tissue samples were collected in glass containers containing formalin and sodium borate from the suspect lesions and submitted to the Laboratory of Tuberculosis, School of Veterinary Medicine, University of Baja California, Mexico and to the United States Department of Agriculture, National Veterinary Services Laboratory in Ames, Iowa, for histopathologic and bacteriologic studies; the laboratory results confirmed mycobacteriosis and the presence of Mycobacterium bovis, respectively. The study herd was selected based on its history of bovine TB and on the willingness of the owner to collaborate in the study. It represents the management styles, environmental conditions, and breed of cattle typically found in northern Baja California, Mexico. A total of 370 Holstein calves (born between July and December 1992) were
Mycobacterium
T.B.R. Evangelista, J.H.D. Anda /Preventive
Veterinary Medicine 27 (1996) 23-27
25
studied in a prospective study that included a TB high risk group and a TB low risk group. Group 1 (high risk) included 91 calves (born in July-August 1992) fed with pooled colostrum (stored frozen at -20°C) from several cows in the study herd during the first 3 days after parturition. In this group, it was unknown if the source of colostrum was cows with previous positive or negative skin-test results; from Days 4 to 60, calves in Grou.p 1 were fed with milk from the bulk tank. Group 2 (low risk) was composed of 279 calves (born between September and December 1992) fed with colostrum (Days l-3) from non-reactor cows allocated in ‘clean pens’ and powdered milk from Days 4 to 60. 2.2. Housing of calves From Days 1 to 60, calves from Groups 1 and 2 were kept separate in two locations in the !same herd. Calves were reared outdoors in individual stalls elevated from the floor. Sixty days after birth, calves in Groups 1 and 2 were segregated in two ‘hot pens’ and four ‘clean pens’, respectively, where they remained for 4 months. At the age of 6 months, all 370 calves were skin-tested using a Mexican bovine PPD. 2.3. The tuberculin test The area of application was cleansed with alcohol (isopropyl 70%) using cotton swabs and paper towel; bovine PPD (0.1 ml) was injected intradermally into the right caudal fold of each calf. The skin-test reaction was palpated 72 + 6 h after application. Positive reactors were defined as any calf in Groups 1 or 2 that showed a response (visual inspection and palpation) to the tuberculin test done by the testing veterinarians (Renteria or Hemandez). A positive reaction to the skin-test (outcome) was considered as an indication of Mycobacterium spp. exposure (USDA, APHIS, VS, Bovine Tuberculosis Eradication, UMR, 1988). 2.4. Analysis The strength of the association between Mycobacterium spp. exposure in calves and management of colostrum and milk (high risk/low risk) was estimated using relative risk. Having a dam which was a skin-test reactor was considered a potential confounder variable and was controlled analytically by stratification following the Mantel-Haenszel procedtue (Fleiss, 1981). Adjusted Mantel-Haenszel odds ratio and chi square test were estimated using a computer statistical program (BMDP, 1990). The relationship between the two risk factors dam skin-test status and colostrum/milk group was also tested for the presence of an interaction effect.
3. Results and discussion A total of 68 (18%) out of 370 calves were classified as positive reactors to the tuberculin test. The Mantel-Haenszel adjusted risk of Mycobacterium spp. exposure
26
T.&R. Evangelisra, J.H.D. Anda /Preuentiue
Veterinary Medicine 27 (1996) 23-27
Table 1 Association between tuberculin skin-test results in Holstein calves and management (high risk vs. low risk), controlling for tuberculin skin-test status of the dam Dam skin-test status
Colostrum
and milk group
Positive Positive Negative Negative Adjusted Mantel-Haenszel
High risk Low risk High risk Low risk odds ratio = 1.9, ,y&
N
TR+ n
30 10 76 19 58 13 201 23 = 3.99, P = 0.0458
of colostrum
and milk
RR
95% CI
1.3 1.o 2.0 1.o
0.1, 2.6
% 33 25 22 11
1.O, 3.6
was 1.9
T.B.R. Evangelista, J.H.D. At&/Preventive
Veterinary Medicine 27 (1996) 23-27
27
Acknowledgements Supported in part by a grant from CONACyT (143M9107) and FOMES SEP in Mexico (93/8083). This report represents a portion of a thesis submitted by the senior author as partial fulfillment of the requirements for the MS degree.
References 1993. Annual Report. Baja California Cattleman’s Association, Baja California Cattleman’s Association, Mexicali, Baja California, Mexico, pp. 9- 10. BMDP Statistical Software, Inc., 1990. BMDP, Los Angeles, CA. Essey, MA., 1990. United States-Mexico Joint Effort for Bovine Tuberculosis Eradication. Proceedings of the 94th Annual Meeting of the United States Animal Health Association, 6-12 October 1993, Las Vegas, NV, Carter Printing Co., Richmond, VA, pp. 543-518. Essey, MA., 1993. Status of the State-Federal Bovine Tuberculosis Eradication Program in the USA; fiscal year 1993. Proceedings of the 97th Annual Meeting of the United States Animal Health Association. Fleiss, J.L., 1981. Statistical Methods for Rates and Proportions. Wiley, New York, 173- 175. Radostits, 0.M. and Blood, D.C., 1985. Herd Health. 1st edn. W.B. Saunders Company, Philadelphia, PA, pp. 116-132. United States Department of Agriculture, Animal and Plant Health Inspection Services, Veterinary Services. Bovine Tuberculosis Eradication. Uniform Methods and Rules (UMR), 3 I March 1988, pp. I- 17.
PFJEVENTNE VETERINARY MEDICINE Preventive Veterinary Medicine 27 (19%) 23-27
Tuberculosis in dairy calves: risk of M’ycobacterium spp. exposure associated with management of colostrum and milk Tom& B. Renteria Evangelista, Jorge HemGndez De Anda
*
Institute de Inuestigaciones en Ciencias Veterinarias, Unioersidad Auto’rwmade Baja California, 21100 Mexicali, BC, Mkxico
Accepted 6 October 1995
Abstract A prospective
study was undertaken to investigate the association between the risk of spp. exposure and management of colostrum and milk in two groups of Holstein calves in a Mycobucterium bouis infected commercial dairy herd in Mexico. Group 1 (high risk) included !>l calves fed with pooled colostrum from several cows in the study herd and raw milk from the bulk tank. Group 2 (low risk) was composed of 279 calves fed with colostrum from tuberculin skin-test negative cows and powdered milk. At 6 months of age, calves in Groups 1 and 2 were skin-tested for detection of Mycobacterium spp. exposure. In the high risk group, 25 (27%) of 91 calves tested positive to the caudal fold skin-test; in the low risk group, 43 (15%) of 279 calves were also classified as positive. After controlling for the confounding effect of skin-test reactor status of dams, it was found that the risk of Mycobucterium spp. exposure was associated with management of colostrum and milk. The adjusted odds for Mycobucterium spp. exposure were 1.9 times higher in the high risk group when compared with the low risk group (P = 0.05). Further, the risk of skin-test reactors increased from 11% in calves born from skin-test negative cows (in the low risk group) to 33% in calves born from skin-test positive cows (in the high risk group).
Mycobacferium
1. Introdluction Bovinie tuberculosis industry.
The disease
(TB) is an important could
cause
important
animal trade
health
issue in the Mexican
complications
* Correstlonding author at: IICV UABC, PO BOX2902, Calexico, CA 92232, USA. 0167-5877/%/$15X@ 0 1996 Elsevier Science B.V. SSDI 0165-5877(95)00573-O
livestock
for the Mexican
dairy
24
T.&R. Evangelista, J.H.D. Andu / Preventive Veterinary Medicine 27 (1996) 23-27
and beef industries. During 1981-1990, based on slaughter surveillance, United States Department of Agriculture investigations have shown that, on average, 67% of all TB cases in cattle in the USA were related to steers of Mexican origin (Essey, 1990). In 1992-1993, Mexico exported about 1300000 steers to the USA. In that period, 299 TB cases in cattle were confirmed in the USA; 210 (70%) of these TB cases were traced back to Mexico. Additionally, it was determined that 137 (65%) of those 210 cases were Holstein steers (Essey, 1993). This finding prompted animal health authorities in Mexico to prohibit the export of Holstein steers of Mexican origin to the USA. In Baja California, Mexico, the dairy cattle population is about 50000 animals kept in approximately 500 dairy farms (about half in only 50 farms). The number of milking cows in commercial dairy farms may range from 100 to 1000 and the daily average milk production per cow may range from 18 lb in the summer to 35 lb in the winter (Baja California Cattleman’s Association, 1993). Currently, strategies to prevent the spread of TB in the dairy cattle population include slaughter surveillance, skin-testing, animal movement restrictions, and, if possible, slaughter of skin-test positive animals, but an indemnity program does not yet exist. Consequently, management practices within herds, such as segregation of infected animals and management of colostrum and milk, have been implemented in some dairy herds to reduce the incidence of the disease. However, in Mexico no epidemiological studies of the relationship between the risk of TB and these management practices have been conducted. The objective of the present study was to estimate the strength of relationship between tuberculin reactor status in Holstein calves and milk feeding management in a Mycobacterium bovis infected commercial dairy herd.
2. Materials
and methods
2.1. Study design In August
1992, all cows (600) in the study herd were skin-tested for detection of spp. exposure, using the caudal fold tuberculin skin-test. Thirty percent of all tested cows were classified as skin-test reactors. Based on this result, cows were separated into ‘hot pens’ for reactor and ‘clean pens’ for non-reactor animals. In October 1992, Mycobacterium bovis was isolated from pleural lesions in a milking cow sent to slaughter. At the abattoir, the carcass was confiscated because of the presence of TB-like lesions. Tissue samples were collected in glass containers containing formalin and sodium borate from the suspect lesions and submitted to the Laboratory of Tuberculosis, School of Veterinary Medicine, University of Baja California, Mexico and to the United States Department of Agriculture, National Veterinary Services Laboratory in Ames, Iowa, for histopathologic and bacteriologic studies; the laboratory results confirmed mycobacteriosis and the presence of Mycobacterium bovis, respectively. The study herd was selected based on its history of bovine TB and on the willingness of the owner to collaborate in the study. It represents the management styles, environmental conditions, and breed of cattle typically found in northern Baja California, Mexico. A total of 370 Holstein calves (born between July and December 1992) were
Mycobacterium
T.B.R. Evangelista, J.H.D. Anda /Preventive
Veterinary Medicine 27 (1996) 23-27
25
studied in a prospective study that included a TB high risk group and a TB low risk group. Group 1 (high risk) included 91 calves (born in July-August 1992) fed with pooled colostrum (stored frozen at -20°C) from several cows in the study herd during the first 3 days after parturition. In this group, it was unknown if the source of colostrum was cows with previous positive or negative skin-test results; from Days 4 to 60, calves in Grou.p 1 were fed with milk from the bulk tank. Group 2 (low risk) was composed of 279 calves (born between September and December 1992) fed with colostrum (Days l-3) from non-reactor cows allocated in ‘clean pens’ and powdered milk from Days 4 to 60. 2.2. Housing of calves From Days 1 to 60, calves from Groups 1 and 2 were kept separate in two locations in the !same herd. Calves were reared outdoors in individual stalls elevated from the floor. Sixty days after birth, calves in Groups 1 and 2 were segregated in two ‘hot pens’ and four ‘clean pens’, respectively, where they remained for 4 months. At the age of 6 months, all 370 calves were skin-tested using a Mexican bovine PPD. 2.3. The tuberculin test The area of application was cleansed with alcohol (isopropyl 70%) using cotton swabs and paper towel; bovine PPD (0.1 ml) was injected intradermally into the right caudal fold of each calf. The skin-test reaction was palpated 72 + 6 h after application. Positive reactors were defined as any calf in Groups 1 or 2 that showed a response (visual inspection and palpation) to the tuberculin test done by the testing veterinarians (Renteria or Hemandez). A positive reaction to the skin-test (outcome) was considered as an indication of Mycobacterium spp. exposure (USDA, APHIS, VS, Bovine Tuberculosis Eradication, UMR, 1988). 2.4. Analysis The strength of the association between Mycobacterium spp. exposure in calves and management of colostrum and milk (high risk/low risk) was estimated using relative risk. Having a dam which was a skin-test reactor was considered a potential confounder variable and was controlled analytically by stratification following the Mantel-Haenszel procedtue (Fleiss, 1981). Adjusted Mantel-Haenszel odds ratio and chi square test were estimated using a computer statistical program (BMDP, 1990). The relationship between the two risk factors dam skin-test status and colostrum/milk group was also tested for the presence of an interaction effect.
3. Results and discussion A total of 68 (18%) out of 370 calves were classified as positive reactors to the tuberculin test. The Mantel-Haenszel adjusted risk of Mycobacterium spp. exposure
26
T.&R. Evangelisra, J.H.D. Anda /Preuentiue
Veterinary Medicine 27 (1996) 23-27
Table 1 Association between tuberculin skin-test results in Holstein calves and management (high risk vs. low risk), controlling for tuberculin skin-test status of the dam Dam skin-test status
Colostrum
and milk group
Positive Positive Negative Negative Adjusted Mantel-Haenszel
High risk Low risk High risk Low risk odds ratio = 1.9, ,y&
N
TR+ n
30 10 76 19 58 13 201 23 = 3.99, P = 0.0458
of colostrum
and milk
RR
95% CI
1.3 1.o 2.0 1.o
0.1, 2.6
% 33 25 22 11
1.O, 3.6
was 1.9
T.B.R. Evangelista, J.H.D. At&/Preventive
Veterinary Medicine 27 (1996) 23-27
27
Acknowledgements Supported in part by a grant from CONACyT (143M9107) and FOMES SEP in Mexico (93/8083). This report represents a portion of a thesis submitted by the senior author as partial fulfillment of the requirements for the MS degree.
References 1993. Annual Report. Baja California Cattleman’s Association, Baja California Cattleman’s Association, Mexicali, Baja California, Mexico, pp. 9- 10. BMDP Statistical Software, Inc., 1990. BMDP, Los Angeles, CA. Essey, MA., 1990. United States-Mexico Joint Effort for Bovine Tuberculosis Eradication. Proceedings of the 94th Annual Meeting of the United States Animal Health Association, 6-12 October 1993, Las Vegas, NV, Carter Printing Co., Richmond, VA, pp. 543-518. Essey, MA., 1993. Status of the State-Federal Bovine Tuberculosis Eradication Program in the USA; fiscal year 1993. Proceedings of the 97th Annual Meeting of the United States Animal Health Association. Fleiss, J.L., 1981. Statistical Methods for Rates and Proportions. Wiley, New York, 173- 175. Radostits, 0.M. and Blood, D.C., 1985. Herd Health. 1st edn. W.B. Saunders Company, Philadelphia, PA, pp. 116-132. United States Department of Agriculture, Animal and Plant Health Inspection Services, Veterinary Services. Bovine Tuberculosis Eradication. Uniform Methods and Rules (UMR), 3 I March 1988, pp. I- 17.