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The control of brucellosis in tropical and subtropical regions
Preventive Veterinary Medicine, 2 (1984) 193--196
193
Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
THE CONTROL OF BRUCELLOSIS IN TROPICAL AND SUBTROPICAL REGIONS PAUL NICOLETTI Department of Preventive Medicine, College of Veterinary Medicine, U n i v e r s i t y of Florida, G a i n e s v i l l e , Florida 32610.
ABSTRACT N i c o l e t t i , P., 1984. The control of b r u c e l l o s i s in t r o p i c a l and subtropical regions. Prev. Vet. Med., 2: 193-196. Brucellosis is perhaps the most widespread and economically important of the zoonotic diseases in t r o p i c a l and subtropical regions. I t s control and eradication are d i f f i c u l t because of many technical and other aspects of the disease. Ancient practices such as nomadism, community grazing by l i v e s t o c k , and modern changes toward larger animal populations and increased commerce cause additional problems. Importation of high producing livestock due to demands f o r additional animal protein create special d i f f i c u l t i e s . Slaughter of valuable diseased animals is often impractical. Reduction of b r u c e l l o s i s under most conditions is best accomplished by widespread use of vaccines. Many modifications of environment, livestock management, social customs and resources w i l l be necessary before many countries can consider eradication programs. INTRODUCTION Much of the land mass in t r o p i c a l and subtropical regions is suited only f o r livestock grazing.
Vast differences e x i s t among countries in t e r r a i n , climate,
social customs, resources, livestock management and a t t i t u d e s toward disease control.
Nomadism, low i n t e n s i t y livestock management, and other practices
make veterinary services d i f f i c u l t .
In recent years, high i n t e n s i t y dairy
c a t t l e units have created special animal health problems. Brucellosis is a major problem confronting food production in t r o p i c a l and subtropical regions of the world. ductivity.
In a d d i t i o n , i t subtracts from human pro-
The prevalence is often high because of close human-animal contacts
and food consumption customs. The problems associated with control of b r u c e l l o s i s can be divided i n t o technical, husbandry, and economic. Technical A most serious d i f f i c u l t y
is the variable incubation period ( N ~ c o l e t t i , 1980).
No s a t i s f a c t o r y method exists to detect animals which are seronegative but which w i l l develop the disease.
Approximately 15% of infected c a t t l e which
shed organisms at p a r t u r i t i o n become p o s i t i v e afterward (O'HaraandChristiansen, 1978; N i c o l e t t i , 1980). 0167-5877/84/$03.00
The figures may be higher among sheep and goats.
© 1984 Elsevier Science Publishers B.V.
194
B r u c e l l o s i s can o n l y be p o s i t i v e l y
diagnosed through l a b o r a t o r y t e s t s .
While a large number and v a r i e t y of procedures are a v a i l a b l e , many problems e x i s t with d i f f e r e n t i a t i o n
of blood serum t i t e r s
vaccines or o t h e r a n t i g e n i c s t i m u l i .
caused by i n f e c t i o n and by
F o r t u n a t e l y , in recent years the expanded
use of s e r o l o g i c t e s t s which q u a l i t a t i v e l y
measure a n t i b o d i e s and the increased
usage of s m a l l e r doses of vaccines have g r e a t l y reduced these d i a g n o s t i c problems. The percentage of l a t e n t i n f e c t i o n s and f a c t o r s which a f f e c t s e x u a l l y immature animals remain unknown.
them among
The occurrence among c a t t l e
but p r o b a b l y g r e a t e r among sheep and goats.
is small
S a t i s f a c t o r y methods f o r d e t e c t i o n
of l a t e n t i n f e c t i o n s have not been developed. Husbandry The types of l i v e s t o c k management which e x i s t in many regions s e v e r e l y restrict
practices for brucellosis control
a p p l i c a b l e to o t h e r s .
For example,
in the United States much progress was made in reducing and e l i m i n a t i n g b r u c e l l o s i s where c a t t l e
herds were small and a c c e s s i b l e .
progress has been slow (Table l )
where herds o f c o w - c a l f management are o f t e n d i f f i c u l t
Table I STATUS OF BRUCELLOSIS ERADICATION PROGRAM 1960-1982 USDA
FY 1960 1961 1962 1963 1964 1965 1966 1967 1968
1969 1970 1971 1972 19'73 1974 1975 1976 1977 1978
1979 19BO 1981 198: >
In recent y e a r s ,
and major problems e x i s t in southern s t a t e s
REACTORS REACTORS • DOLLARS (%) (in thous<]nds) (in millions) I .19 166 148 1.04 140 1914 1.06 27 192 1.17 19.4 32 1~5 19.,5 35 1~2 29 20.5 1.04 21 2016 1.24 47 2LO ~ 24 149 21.7 I .20 I~O 20.5 I. 16 119 21.7 1.10 116 ~6.6 1.05 124 188 1.16 158 ;'1.5 I .34 196 24.6 1.46 250 30.8 1.29 283 36.8 1.14 236 42.7 241 54.6 I.I 6 1.12 197 ,59,9 195 1.09 74. 6 193 .99 90.5 176 .91 90.5
to assemble,
195
In many countries large concentrated dairy units have been developed often by importing expensive c a t t l e (Fig. I ) .
Brucellosis control is d i f f i c u l t
due
to exposure to i n f e c t i ~ of highly susceptible cows. Test and slaughter methods are often f u t i l e and the sale of diseased c a t t l e is impractical.
Fig. 1 - High i n t e n s i t y dairy units are increasing in t r o p i c a l and subtropical regions. Other husbandry practices in tropical and subtropical regions which cause difficulties
are community grazing, nomadism, and livestock commerce. Segre-
gation of purchased animals or at p a r t u r i t i o n is often impractical. Economic Organized control programs through governments are expensive and s u f f i c i e n t resources are often not a v a i l a b l e .
These may be laboratory f a c i l i t i e s ,
vehicles,
trained personnel, and assistance f o r replacement of diseased livestock.
Each
country must thoroughly assess the costs and benefits of whatever e f f o r t s are made. The owners of livestock must be convinced of economic advantages f o r any organized program to succeed. Vaccination Most workers agree that the smooth l i v e organisms of Brucella abortus Strain 19 and B. melitensis Rev 1 have many advantages over inac t iv at ed vaccines. Their l i m i t a t i o n s , including interference with diagnostic tests, are well known. However, they provide good protection on a herd or f loc k basis by reducing c l i n i c a l symptoms (exposure p o t e n t i a l ) and elevating resistance.
Their use
under many conditions should be expanded to include sexually mature animals. The reduced doses also reduce the physiologic and serologic effects.
I t is
i l l o g i c a l to r e s t r i c t the use of vaccines among mature animals where there are
1@6 no controls on infected populations. ERADICATION vs. CONTROL The e r a d i c a t i o n of animal diseases is a popular idea and a j u s t i f i c a t i o n
for
an organized program is made t h a t the goal is worthy of the means. While t h i s is l o g i c a l in some diseases and under c e r t a i n c o n d i t i o n s , the c r i t e r i a which are necessary f o r success cannot be ignored.
Comparisons should not be made
between diseases or d i s s i m i l a r conditions. Eradication of b r u c e l l o s i s is an enormous committment to c o n t r o l s of l i v e stock commerce, money, patience, and adaptation. t r o p i c a l and s u b t r o p i c a l regions which can f u l f i l l
There are few countries in t h i s committment.
Control
should be an acceptable philosophy and whatever measures are applied should be aimed at reducing b r u c e l l o s i s to the lowest level possible using a v a i l a b l e resources. REFERENCES N i c o l e t t i , P., 1980. The epidemiology of bovine b r u c e l l o s i s . and Comp. Med., 24:69-98.
Adv. Vet. Sci.
O'Hara, P.J. and Christiansen, K.H., 1978. I n v e s t i g a t i o n of abortions in b r u c e l l o s i s tested herds. N.Z. Vet. J . , 26:70-73.
193
Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
THE CONTROL OF BRUCELLOSIS IN TROPICAL AND SUBTROPICAL REGIONS PAUL NICOLETTI Department of Preventive Medicine, College of Veterinary Medicine, U n i v e r s i t y of Florida, G a i n e s v i l l e , Florida 32610.
ABSTRACT N i c o l e t t i , P., 1984. The control of b r u c e l l o s i s in t r o p i c a l and subtropical regions. Prev. Vet. Med., 2: 193-196. Brucellosis is perhaps the most widespread and economically important of the zoonotic diseases in t r o p i c a l and subtropical regions. I t s control and eradication are d i f f i c u l t because of many technical and other aspects of the disease. Ancient practices such as nomadism, community grazing by l i v e s t o c k , and modern changes toward larger animal populations and increased commerce cause additional problems. Importation of high producing livestock due to demands f o r additional animal protein create special d i f f i c u l t i e s . Slaughter of valuable diseased animals is often impractical. Reduction of b r u c e l l o s i s under most conditions is best accomplished by widespread use of vaccines. Many modifications of environment, livestock management, social customs and resources w i l l be necessary before many countries can consider eradication programs. INTRODUCTION Much of the land mass in t r o p i c a l and subtropical regions is suited only f o r livestock grazing.
Vast differences e x i s t among countries in t e r r a i n , climate,
social customs, resources, livestock management and a t t i t u d e s toward disease control.
Nomadism, low i n t e n s i t y livestock management, and other practices
make veterinary services d i f f i c u l t .
In recent years, high i n t e n s i t y dairy
c a t t l e units have created special animal health problems. Brucellosis is a major problem confronting food production in t r o p i c a l and subtropical regions of the world. ductivity.
In a d d i t i o n , i t subtracts from human pro-
The prevalence is often high because of close human-animal contacts
and food consumption customs. The problems associated with control of b r u c e l l o s i s can be divided i n t o technical, husbandry, and economic. Technical A most serious d i f f i c u l t y
is the variable incubation period ( N ~ c o l e t t i , 1980).
No s a t i s f a c t o r y method exists to detect animals which are seronegative but which w i l l develop the disease.
Approximately 15% of infected c a t t l e which
shed organisms at p a r t u r i t i o n become p o s i t i v e afterward (O'HaraandChristiansen, 1978; N i c o l e t t i , 1980). 0167-5877/84/$03.00
The figures may be higher among sheep and goats.
© 1984 Elsevier Science Publishers B.V.
194
B r u c e l l o s i s can o n l y be p o s i t i v e l y
diagnosed through l a b o r a t o r y t e s t s .
While a large number and v a r i e t y of procedures are a v a i l a b l e , many problems e x i s t with d i f f e r e n t i a t i o n
of blood serum t i t e r s
vaccines or o t h e r a n t i g e n i c s t i m u l i .
caused by i n f e c t i o n and by
F o r t u n a t e l y , in recent years the expanded
use of s e r o l o g i c t e s t s which q u a l i t a t i v e l y
measure a n t i b o d i e s and the increased
usage of s m a l l e r doses of vaccines have g r e a t l y reduced these d i a g n o s t i c problems. The percentage of l a t e n t i n f e c t i o n s and f a c t o r s which a f f e c t s e x u a l l y immature animals remain unknown.
them among
The occurrence among c a t t l e
but p r o b a b l y g r e a t e r among sheep and goats.
is small
S a t i s f a c t o r y methods f o r d e t e c t i o n
of l a t e n t i n f e c t i o n s have not been developed. Husbandry The types of l i v e s t o c k management which e x i s t in many regions s e v e r e l y restrict
practices for brucellosis control
a p p l i c a b l e to o t h e r s .
For example,
in the United States much progress was made in reducing and e l i m i n a t i n g b r u c e l l o s i s where c a t t l e
herds were small and a c c e s s i b l e .
progress has been slow (Table l )
where herds o f c o w - c a l f management are o f t e n d i f f i c u l t
Table I STATUS OF BRUCELLOSIS ERADICATION PROGRAM 1960-1982 USDA
FY 1960 1961 1962 1963 1964 1965 1966 1967 1968
1969 1970 1971 1972 19'73 1974 1975 1976 1977 1978
1979 19BO 1981 198: >
In recent y e a r s ,
and major problems e x i s t in southern s t a t e s
REACTORS REACTORS • DOLLARS (%) (in thous<]nds) (in millions) I .19 166 148 1.04 140 1914 1.06 27 192 1.17 19.4 32 1~5 19.,5 35 1~2 29 20.5 1.04 21 2016 1.24 47 2LO ~ 24 149 21.7 I .20 I~O 20.5 I. 16 119 21.7 1.10 116 ~6.6 1.05 124 188 1.16 158 ;'1.5 I .34 196 24.6 1.46 250 30.8 1.29 283 36.8 1.14 236 42.7 241 54.6 I.I 6 1.12 197 ,59,9 195 1.09 74. 6 193 .99 90.5 176 .91 90.5
to assemble,
195
In many countries large concentrated dairy units have been developed often by importing expensive c a t t l e (Fig. I ) .
Brucellosis control is d i f f i c u l t
due
to exposure to i n f e c t i ~ of highly susceptible cows. Test and slaughter methods are often f u t i l e and the sale of diseased c a t t l e is impractical.
Fig. 1 - High i n t e n s i t y dairy units are increasing in t r o p i c a l and subtropical regions. Other husbandry practices in tropical and subtropical regions which cause difficulties
are community grazing, nomadism, and livestock commerce. Segre-
gation of purchased animals or at p a r t u r i t i o n is often impractical. Economic Organized control programs through governments are expensive and s u f f i c i e n t resources are often not a v a i l a b l e .
These may be laboratory f a c i l i t i e s ,
vehicles,
trained personnel, and assistance f o r replacement of diseased livestock.
Each
country must thoroughly assess the costs and benefits of whatever e f f o r t s are made. The owners of livestock must be convinced of economic advantages f o r any organized program to succeed. Vaccination Most workers agree that the smooth l i v e organisms of Brucella abortus Strain 19 and B. melitensis Rev 1 have many advantages over inac t iv at ed vaccines. Their l i m i t a t i o n s , including interference with diagnostic tests, are well known. However, they provide good protection on a herd or f loc k basis by reducing c l i n i c a l symptoms (exposure p o t e n t i a l ) and elevating resistance.
Their use
under many conditions should be expanded to include sexually mature animals. The reduced doses also reduce the physiologic and serologic effects.
I t is
i l l o g i c a l to r e s t r i c t the use of vaccines among mature animals where there are
1@6 no controls on infected populations. ERADICATION vs. CONTROL The e r a d i c a t i o n of animal diseases is a popular idea and a j u s t i f i c a t i o n
for
an organized program is made t h a t the goal is worthy of the means. While t h i s is l o g i c a l in some diseases and under c e r t a i n c o n d i t i o n s , the c r i t e r i a which are necessary f o r success cannot be ignored.
Comparisons should not be made
between diseases or d i s s i m i l a r conditions. Eradication of b r u c e l l o s i s is an enormous committment to c o n t r o l s of l i v e stock commerce, money, patience, and adaptation. t r o p i c a l and s u b t r o p i c a l regions which can f u l f i l l
There are few countries in t h i s committment.
Control
should be an acceptable philosophy and whatever measures are applied should be aimed at reducing b r u c e l l o s i s to the lowest level possible using a v a i l a b l e resources. REFERENCES N i c o l e t t i , P., 1980. The epidemiology of bovine b r u c e l l o s i s . and Comp. Med., 24:69-98.
Adv. Vet. Sci.
O'Hara, P.J. and Christiansen, K.H., 1978. I n v e s t i g a t i o n of abortions in b r u c e l l o s i s tested herds. N.Z. Vet. J . , 26:70-73.