Brucellosis in Argentina

Veterinary Microbiology 90 (2002) 71±80

Brucellosis in Argentina Luis E. Samartino* Institute of Pathobiology, National Institution of Livestock and Agriculture Research (INTA), CICVyA, pob C.C. 77, Castelar, Buenos Aires 1712, Argentina

Abstract Brucellosis has been recognized in Argentina since the 19th century. Several studies demonstrated the presence of the disease in most of the domestic species. Actually, the estimate of prevalence is that between 10 and 13% of the farm animals are infected with bovine brucellosis with an individual rate of 4±5%. The annual economical losses have been estimated at US$ 60,000,000. The control of bovine brucellosis began in 1932 and successive resolutions have been issued since then. The current resolution indicates that B. abortus S19 is mandatory in female calves between 3 and 8 months of age. The vaccine strain B. abortus RB51 was provisionally approved but only for cattle older than 10 months of age. The brucellosis control program consists principally of test and slaughter. This methodology has been successful mainly in the dairy farms that have the incentive due to increased pricing because of obtaining a low prevalence of the disease. Brucellosis has been found in porcine, caprine, ovine and canine species. All Brucella species have been found in the country. Human brucellosis is an important disease and a national coordinated diagnostic net has been formed to better control the disease in man. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Argentina; Brucellosis; Vaccine; B. abortus S19; B. abortus RB51

1. Introduction Argentina is located in the south of South America. The national territory has an area of 2,791,810 km2 and a population of 37,000,000 inhabitants. The country has ®ve geographical regions characterized by major diversities (weather, industries, livestock, agriculture, etc.), but I will comment here only on the livestock distribution (Table 1). Argentinean beef is very well recognized world wide. In 1998, Argentina ranked 9th in meat exportation in the world. Actually, the cattle population is around 50,000,000 with 14,000,000 slaughtered per year. The national consumption of beef is around 63 kg per inhabitant per year (INTA, 2000). * Tel.: ‡54-11-4621-1712. E-mail address: [email protected] (L.E. Samartino).

0378-1135/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 1 1 3 5 ( 0 2 ) 0 0 2 4 7 - X

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Table 1 Livestock population in the Argentine Republic (in millions) Regions Species

Bovine Porcine Ovine Caprine

Regions

Total

Humid Pampa

Northwest

Northeast

Cuyo

Patagonia

38 1.7 3 0.5

1.73 0.4 1.20 1

7.74 0.2 1.40 0.2

1.40 0.1 1.35 1

0.80 0.04 8 1.3

49.67 2.44 14.95 4.00

Source: INTA (2000).

On the other hand, the production of milk is approximately 9450 billions l per year (1988) produced from 2,400,000 bovines. The pork meat industry is very poor in Argentina with 2,500,000 animals dedicated to local consumers. Caprines are mainly concentrated in the northwest of the country, however, in recent years, dairy goat herds were increasing in Buenos Aires Province, due to the high demands by consumers for goat milk cheese. Ovine production has decreased dramatically in the last decade mainly due to low economic conditions for the wool business. Sheep are concentrated preferentially in the south and the northeast of the country (INTA, 2000). 2. Generalities of brucellosis in Argentina Most of the contributions to the knowledge of brucellosis in Argentina are due to three institutions. The Pan-American Zoonoses Center (CEPANZO), brucellosis unit, located in Buenos Aires until 1992, made an important contribution to studying brucellosis not only in Argentina but for all the Latin-American countries. The National Service of Animal Health (SENASA) has been in charge of the rules and regulations for the control and eradication of animal brucellosis. The National Institution of Livestock and Agriculture Technology (INTA) through its laboratories located in Castelar, Buenos Aires have performed studies in animal brucellosis since 1956; they do basic and applied research which characterized the distribution of Brucella species as well the prevalence of the disease in different regions. In the early 1980s, several animal health units were built in different INTA experimental stations, improving signi®cantly the local investigations in brucellosis. During the last decade, most of the veterinary schools in the country also promoted the inclusion of brucellosis groups in their staff. In addition, the National Institute of Microbiology ``Carlos Malbran'' has intensi®ed the investigation of human brucellosis in Argentina including the building of a laboratory network throughout the country. 3. Bovine brucellosis Brucellosis has been known in Argentina since the 19th century. There are many descriptions of the disease that con®rm the presence of animal brucellosis in Argentine

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herds. The ®rst report of an isolation of a B. abortus strain from a milk of a cow was done in 1925 (Carrillo, 1990). All surveys done around the middle of the 20th century described a prevalence of 20% in dairy cattle and 18% in slaughterhouses. In the middle of the last century, bovine brucellosis has been detected in most of the Argentine provinces. In 1960s, INTA did several studies in different regions of the country and demonstrated an incidence of 25% for dairy cattle and 20% for beef cattle. Other surveys done in the 1970s indicate that the prevalence in several Argentine provinces ranged from 10% in Santa Fe, between 10 and 25% in Buenos Aires and 11% in La Pampa and 28% in the northwest. Partial investigations done between 1981 and 1989 in those provinces, where the cattle concentration is lower than the Pampas, showed prevalences between 0.3 and 3.72% (Carrillo, 1990). Based on partial surveys, the prevalence in cattle was more than 10% estimated in 1985. It should be noted that this statistic corresponds to infected farms, however, the individual infection rate was sporadically above 5%. In Buenos Aires Province, a survey conducted between 1994 and 1998 with 53,200 bovine sera demonstrated 5.6% prevalence (INTA, 2000). The current estimation of the prevalence of the disease in cattle is that between 10 and 13% of the farms are infected and the individual rate is between 4 and 5%. In 1998, the milk industry decided to differentiate the prices of the milk obtained from brucellosis free herds. This measure-induced dairy cattleman to improve the sanitary status of their herds allowing to decrease the prevalence of the disease in this category. Actually, the individual prevalence for dairy cattle in the country is estimated between 2 and 2.5%. Santa Fe Province with approximately 6,000,000 dairy cattle has prevalence below 1.5%. In beef cattle, individual rate is between 2 and 6% according to partial surveys and country reports. Generally speaking, there is no requirement for the identi®cation of Brucella species by an accredited veterinarian, however, intensive courses and continuous education trough regional and local meetings, publications, etc. show an increase of samples sent to laboratories for bacteriological diagnosis. Actually, most of the isolates correspond to B. abortus biovar 1, however, B. abortus biovar 2 is also found. Previously, B. suis could also be isolated from cattle produced by small producers in suburban areas of the countries due to common practice of raising cattle and swine in close contact. Recently, the ®rst isolation of B. abortus biovar 1 from buffalo was reported in the northeast of the country. The economical losses due to brucellosis in cattle have been estimated in US$ 60,000,000 per year (SENASA, 1999). 4. Legislation of bovine brucellosis The regulation of the control and prevention of the brucellosis in Argentina began in 1932, when by law the disease was de®ned as an occupational disease. During 1947, a resolution was passed to voluntary apply the B. abortus Strain 19 vaccine against brucellosis in cattle. In 1952, a new ministerial resolution indicated that all breeding domestic species must be screened with a diagnostic test for brucellosis. In 1955, those tests were regulated for imported animals. In 1958, another resolution was passed that regulated the registration of vaccines and antigens for prevention and diagnosis of brucellosis, respectively. In 1980, the Department of Agriculture required that B. ahortus

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S19 vaccination be compulsory in calves of 3±8 months of age excluding the Patagonia in the south of Argentina. In 1982, the Agriculture Department (Resolution 83/72) issued a new resolution (SENASA, 1982). This resolution became the ®rst integrated program of the country and included the participation of federal and states agriculture of®ces, government and private veterinarians and producers. The program was divided into two parts, a voluntary eradication and a mandatory eradication part based on previous epidemiological studies. A complete description of the procedures for vaccination was provided. The mandatory calf-hood vaccination and identi®cation of all female cattle between 3 and 8 months of age in all the Argentine territories was required. The vaccinations must be done either by federal or private veterinarians. The B. abortus Strain 19 was given subcutaneously using at least 50 billion live organisms. Adult vaccination was not authorized under any circumstance. In order to be moved between territories, the cattle should have an individual registration number and a certi®cation of vaccination. In 1989, the of®cial dose of S19 was reduced to 10  109 live organisms. The number of vaccinated calves increased from 33.7% in 1980 to 70±74% in the following years and reached 85% in cattle raised in the Pampas. This level of vaccination remained constant until the beginning of the 1990s. The resolution also included testing requirements and procedures for the diagnostic of bovine brucellosis. Standard plate and tube agglutination tests as well as the 2-mercaptoethanol test were done routinely. The complement ®xation test was used as a supplemental test. In dairy farms, a ring test was used for surveillance. During the 1980s, most of the diagnostic tests were conducted in ``of®cial'' laboratories and in few privates laboratories. In spite of the quality of the integrated program, diverse reasons induced it to fail. This mainly stemmed from economic problems in the livestock industry that do not allow to compensate to the cattleman to eliminate their infected cattle. In 1988, INTA developed a ``strategic model for eradicating brucellosis in an infected county in Buenos Aires Province''. This model demonstrated that by using all available tools against bovine brucellosis and with the participation of federal and local authorities, private veterinarians and producer associations, it is possible to eliminate the disease without important economic losses for the producer (Villa et al., 1995). In 1993, the Agriculture Department promoted a new resolution (1269/3) replacing the one written in 1982 (SENASA, 1993). The following were the main modi®cations.     

Modify the age of calf vaccination from 3±8 to 3±10 months of age. Require certification of brucellosis free herds, duration of the status, and a testing period. Require mandatory accreditation of private veterinarians. Incorporate the buffer plate agglutination test as a screening test and elimination of the standard plate test (SENASA, 1995). Authorization for adult vaccination with S19 under SENASA supervision.

In the late 1980s, the use of reduced B. abortus S19 dose began. However, the management of this vaccine was not well controlled. For example, ®eld veterinarians made the ``reduced dose'' by themselves without any controls or con®rmation by colony counting. It was a common practice to vaccinate with 1 ml of the full doses in herds where

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Fig. 1. Distribution of S19 vaccinated calves through the years in Argentina. Notice the important increase of number of vaccinated animals after 1985 when the compulsory vaccination began in the country. The average of female calves available has been around 5,600,000. Source: SENASA. The no. of vaccines in the year 1976 were 836,744; 1980: 1,768,695; 1985: 3,912,781; 1990: 3,150,633; 1991: 2,807,940; 1992: 2,890,191; 1993: 3,226,133; 1994: 3,768,480; 1995: 4,378,879; 1996: 5,538,274; 1997: 4,590,120; 1998: 5,414,096; 1999: 4,390,198; 2000: 5,444,684.

brucellosis was present mainly in order to ``stop abortions''. This practice resulted in confounding serological results and also invalid high estimates of prevalence. An important development occurred in the second-half of the 1990s. Cattle were immunized to control foot and mouth disease using a vaccine having oil as adjuvant. Controversial information became disseminated and claimed that such a vaccine interfered with the protection afforded by B. abortus S19 if both were applied simultaneously. Under such circumstances, INTA conducted a study that demonstrated the foot and mouth vaccine did not interfere with the protection afforded by B. abortus S19 (Samartino et al., 1999). This information helped increase calf vaccination for brucellosis to more than 90% of female calves (SENASA, 1998) (Fig. 1). Applying this management allowed the cattleman to reduce the costs of vaccination because the veterinarian goes once to the farm and vaccinates for both the diseases and also the animals are bringing once the shut. In 1998, a conditional authorization was issued for the use of the vaccine B. abortus RB51 under strict veterinary supervision in female cattle older than 10 months of age and not more than 3 months of pregnancy. This regulation was based on studies done in Argentina, where the B. abortus RB51 did not increase the serological titers although adult cattle was previously calf-hood vaccinated with S19. Beside, strain RB51 did not induce abortions even when it is applied to the pregnant cattle. The application of B. abortus RB51 vaccine can be performed by an accredited veterinarian based on their knowledge of the

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brucellosis status of the herd. Beside the capability of this vaccine to induce effective immunity in adult cattle without producing confounding O-side antibodies, it has been shown to effectively substitute for the reduced vaccine dose of S19. Actually, two experiments were conducted by government researchers and the manuscripts are under preparation. However, in a practical application on farms where bovine brucellosis was a severe problem, revaccination with B. abortus RB51 contributed to the eradication of the disease from those herds. It should be noted that several laboratories produce the S19 vaccine in Argentina whereas B. abortus RB51 is imported from USA at a signi®cantly higher cost. The program adopted to induce private veterinarians to have a major participation in controlling bovine brucellosis as well the number of private laboratories performing diagnosis has worked well. Previously, veterinarians did the screening test themselves and sent those positives to the laboratories for classi®cation. However, in order to declare a herd brucellosis free, all tests must be done in an of®cial laboratory. The third National Control and Eradication Program was begun in 1999 by the Agriculture Department (resolution 115/99) and a National Commission of Brucellosis and Tuberculosis was created. This group is composed by individuals from all sectors involved in livestock industries, research institutions, veterinary and cattleman associations, universities, etc. and is coordinated by the SENASA. Their strategies that complement the previous resolutions are:  

     

Coordination of activities at the regional and local levels (county) by conformation to the Local Sanitary Units. Review of program 3 years after being issued. In order to monitor the progress of the program, it was proposed that herd prevalence is serologically evaluated through a representative provincial sanitary commission. When this evaluation has been accomplished, the program will be reviewed and alternative strategies may be considered. Registration of accredited veterinarians (must take an approved course). Accreditation of private laboratories in order to issue valid results for certifications of herds as brucellosis free. All the laboratories must be audited by the National Service of Animal Health. Build a national net of accredited laboratories for the diagnosis of brucellosis; to date, 290 private laboratories are in the net. All serological tests must be done exclusively in accredited laboratories. Mandatory identification of all animals. Mandatory vaccination of 3±8 months old female calves with B. abortus S19. Vaccination with B. abortus RB51 follows previous status without modification. Categorization of the farms regarding the sanitary status:  ``herds under control'' on farms where all animals were bled once regarding the results;  ``controlled herds'' on those farms where no reactors were detected and an official testing with negative results is pending;  ``brucellosis free herd'' certification corresponds to those farms where all cattle are negative and the official brucellosis free certificate was issued by the SENASA.

According to the latest data, there are 11,865 beef farms and 5629 dairy farms under the status ``herds under control'' and 320 beef farms and 959 dairy farms under the status

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Table 2 Number of bovines and farms certified brucellosis free in Argentina Total bovines Dairy cattle Beef cattle

Mix farms

Total farms

Dairy farms

Beef farms

Mix farms

1,360,992

26,977

6374

5469

765

140

1,229,542

104,473

December 2001, Source: SENASA.

``controlled herds''. According to these data, there are actually 28,752,437 bovines involved in brucellosis control including all respectively categorization (SENASA news, No. 43, December 2001) (Table 2). Actually, new modi®cations are being considered for implementation based on the regional differences of the country. Dairy farms will have four milk ring tests and a serological test annually and beef cattle must have an annual serological test. Vaccination will be increased and controlled. The movement of the cattle intended for breeding will be restricted to those animals that can be shown to originate from brucellosis negative herds having a certi®cation of vaccination. Competitive ELISA and ¯uorescent polarization (sera) and indirect ELISA (milk) have been validated and their use as alternative diagnostic tests will be implemented. In 1966, a strict quality control of the vaccine and antigen production for the use in animal brucellosis was instituted. Every batch of antigen and vaccine (national and foreign) produced either by private or government laboratories have to be manufactured under controlled conditions and authorized for commercialization by SENASA. 5. Brucellosis in other species Caprine brucellosis has been studied since 1940, when the ®rst reports were received estimating a prevalence of 20%. Further surveys in the northwest of the country showed an infection rate of 20±25%. Studies done in the Salta Province showed 14.9% reactors. A survey done in San Luis showed 4.5% prevalence. In 1993, an outbreak occurred in a farm with 2300 goats in the Province of Mendoza. The infection rate was higher than 50% and 26 persons became infected (Wallach et al., 1998). Surveys in the last 3 years showed that between 0.5 and 0.8% prevalence of caprine brucellosis in the Provinces of Tucuman and Catamarca and La Rioja. It is noteworthy that the brucellosis prevalence found in animals located in the valley is lower than those animals located in the mountains. This fact can be explained, as the goats in the valley are raised using more stringent condition with a better sanitary control whereas the mountain goats still have the nomad habitat where continuous contact among the herds exists. Despite the fact that caprine brucellosis is well recognized, the use of REV 1 vaccine is not authorized in Argentina. Rose Bengal and BPA are used as screening test and 2mercaptoethanol as a con®rmatory test. Recently, indirect ELISA and ¯uorescent polarization have been demonstrated to be excellent tools for the diagnostic of caprine brucellosis. B. melitensis biovar 1 is isolated from infected goats.

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Swine brucellosis has also been studied since the 1940s. INTA conducted several studies on porcine brucellosis focusing mainly on establishing regional prevalences and experiments for developing a vaccine. Between 1960 and 1980, several surveys found 14.2±25% prevalence. Actually, there is no formal program of monitoring porcine brucellosis, however, industrial breeders keep doing serological tests to control the disease of their animals. One frequently ®nds reactors in those animals located in suburban areas where the owner kept a few animals for his consumption or where small enterprises raised pigs for local business. Serological diagnosis is done using the same tests applied for caprine brucellosis. B. suis biovar 1 is frequently isolated from pigs. However, it is also common to ®nd B. suis which is considered atypical because the strain does not correspond to the current classi®cation. This strain induces a high percentage of abortions and causes severe lesions to limphatic tissue (spleen, liver, limphonodules) when it is inoculated to guinea pigs. Ovine brucellosis was found in all the regions where sheep are located. It was a common practice to examine the epididymous of the rams in order to show they were free of lesions. Later, the agar diffusion test was used to complete the diagnosis and also the CF test. Surveys done in Buenos Aires Province found that 28.6% of sheep were not recommendable for breeding; this result was con®rmed in other surveys done by CEPANZO (Carrillo, 1990). In the Argentinean Patagonia and the northeast of the country, INTA Bariloche and INTA Mercedes, Corrientes has conducted several surveys of those regions and found as high as 25% of the rams were infected. Recently, the indirect ELISA was adopted in federal laboratories to improve the diagnostic ef®cacy. B. melitensis in ovine is not a major problem in Argentina although few cases have been described. Brucella ovis is isolated mainly from rams but can also be found in contaminated ewes. Brucellosis was also con®rmed in other domestic animals. Brucellosis in dogs is found occasionally in urban populations. The common practice of dog's breeders to purchase male studs increased the dissemination of the disease. The isolation of Brucella canis has been very common in recent years. Actually, those breeders who know the presence of the disease, keep close control of their animals and request a serological test before mating their animals. Even in the suburban areas of the main cities, canine brucellosis prevalence is important. Most of the ranches in the country have dogs, however, the presence of canine brucellosis is almost nil. Sometimes dogs are positive for B. abortus or B. suis, and B. abortus can be found sporadically in horses. There have not been major surveys to identify wild-life reservoirs of brucellosis in the country. However, B. abortus was isolated from foxes, weasel and ferrets and B. suis was isolated from European hare (Acha and Szyfres, 1986). 6. Zoonotic aspect of the disease Human brucellosis has been extensively studied in Argentina. It was ®rst described in 1922 and B. melitensis was ®rst isolated from a patient reported in 1930 (Molinari, 1951). In 1932, the National Commission for the Study of Undulant Fever was created and described the disease according to its geographical origin. It was designated western brucellosis when the disease was linked to the infections in goats and eastern brucellosis

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when the infections were due to B. abortus or B. suis. In 1950, not less than 300 papers regarding human brucellosis were published and a few National Conferences of Human Brucellosis were held. One report mentioned that between 1945 and 1976, 157 strains of B. abortus, 20 strains of B. suis and 22 strains of B. melitensis were isolated from 714 cases of brucellosis involving 185 farm workers and 152 slaughterhouse employers (Carrillo, 1990). Another report showed in 1985 that 53% of the strains isolated from humans were B. suis. The disease was found mainly in slaughterhouse employees and farm workers. Between 1993 and 1995, 212 cases of human brucellosis were detected of which 88 originated from cattle, 57 from pigs and 31 from goats. One hundred and eighteen of these cases were detected in rural areas and 18 in urban areas and associated with contaminated goat-cheese. It should be noted that it was also an increase of human infection due to autoinoculation with B. abortus S19 (Wallach et al., 1995; Gil and Samartino, 2000). Although the incidence of canine brucellosis is high, few cases were reported in which B. canis was isolated from humans. Actually, human brucellosis remains an important disease that persists in regions where the infection in animals has not been brought under control and the number of the cases reported is likely underestimated from remote regions. However, it should be noted that important efforts have been made by local and national services such as the Institute of Microbiology in providing assistance and coordinating a diagnostic net in almost all Argentinean Provinces. 7. Final remarks Despite the presence of control programs that have been in place for many years, the control of bovine brucellosis has yet to be accomplished in Argentina. It is very important to stress that in Argentina, the brucellosis control programs have always been based on a test and slaughter policy. The efforts and money expended by the producers is very high. The price paid for a reactor is half of the price of a negative animal. This fact induce to the producers to keep positive animals in the farms looking for a better price. Although this cattle is separated to the main herd, the risk of the spread bacteria to susceptible animals is high. Besides, this measure also increases the cost of the eradication of the disease. The continuous economical constraints do not allow the government to use one of the most powerful tools to eradicate any disease, that of indemni®cation. The regional programs should be responsible for the overall coordination of the vaccination campaigns, the monitoring the status of herds, evaluation of data and planning of follow-up strategies according to the particular regional conditions. There is a need for increasing the awareness of both Ministries of Health and as well as the Veterinary Public Health Service regarding to human brucellosis. A collaboration between both these units is essential for the success of any control program (Gil and Samartino, 2000). Producers have demonstrated a very strong interest in eradicating animal brucellosis from their herds as evidenced by the decreased incidence of brucellosis in dairy herds. However, the efforts and ®nancial burden that have to be made to reach this accomplishment are too high to be born by the local producer without federal support. I presented here a brief summary of the epidemiological and control aspects regarding brucellosis in Argentina. I understand that the importance of the disease for the Argentinean

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scienti®c community is well appreciated. Finally, I must recognize the efforts of those professionals (scientists, federal and private veterinarians, physicians, etc.) who dedicate almost their entire scienti®c lives to the study brucellosis in Argentina. References Acha, F., Szyfres, B., 1986. Brucellosis. In: Zoonosis y enfermedades transmisibles comunes al hombre y a los animales. Pan-American Health Organization (PAHO), pp. 14±36. Carrillo, C.G., 1990. Animal and human brucellosis in the Americas. Office Internacional des Epizooties, pp. 4± 30. Gil, A., Samartino, L., 2000. Zoonosis en los sistemas de produccioÂn animal de las areas urbanas y periurbanas de AmeÂrica Latina. Livestock Policy Discussion Paper No 2. Food and Agriculture Organization. Instituto Nacional de Tecnologia Agropecuaria (INTA), 2000. Documento del Programa de Salud Animal, Mimeo, 85 pp. Molinari, H., 1951. Historia de la brucelosis en la Republica Argentina. Rev. Assoc. Med. Argent. 61, 64±69. Samartino, L.E., Fort, M., GonzaÂlez TomeÂ, J., Marduel, M., Piazza, E., Salustio, E., Gregoret, R., 1999. EvaluacioÂn de la proteccioÂn antibruceÂlica otorgada por la cepa 19 en bovinos vacunados simultaÂneamente con vacuna antiafiosa oleosa. Rev. Med. Vet. 80 (3), 186±189. Servicio Nacional de Sanidad Animal (SENASA), 1982. Programa Nacional de control y erradicacioÂn de la brucelosis bovina. ResolucioÂn 73/82. Mimeo, 32 pp. Servicio Nacional de Sanidad Animal (SENASA), 1993. Programa de control y erradicacioÂn de la brucelosis bovina. ResolucioÂn 1269/3. Mimeo, 20 pp. Servicio Nacional de Sanidad Animal (SENASA), 1995. Manual de procedimientos Diagnostico serologico de la brucelosis bovina. Mimeo, 66 pp. Servicio Nacional de Sanidad y Calidad Agroalimentaria (SENASA), 1999. Plan Nacional de Control y Erradicacion de Brucelosis y Tuberculosis bovina. ResolucioÂn 115/99. Mimeo, 62 pp. Villa, L., Saravi, M., GonzaÂlez TomeÂ, J., Carrillo, B., 1995. Modelo de estrategia para el control de la brucelosis bovina en el partido de Suipacha. Rev. Soc. Med. Vet. 76 (5), 282±287. Wallach, J., Lucero, N., Efron, A., Casimir, L., Baldi P., 1995. Estudjo seroepidemioloÂgico en infecciones humanas por Brucella. Congreso Argentino de Zoonosis. Congreso Latinoamericano de Zoonosis. Buenos Aires, Argentina. Wallach, J., Samartino, L., Efron, A., Baldi, P., 1998. Human infection by Brucella melitensis: an outbreak attributed to contact with infected goats. FEMS Immunol. Med. Microbiol. 19, 315±321.