R.A.M.S. Silva & A. M. R. Dávila
References
Laboratory of Ecopathology, EMBRAPA/CPA-Pantanal E: mail: [email protected]
Trypanosoma vivax was reported in the New World for the first time in French Guyana (Leger and Vienne, 1919), and later in others parts of South America, Central America, and some Caribbean islands (Melendez et al., 1995). In Brazil, Shaw and Lainson (1972), reported the first occurence of T. vivax. The parasite was observed in a water buffalo (Bubalis bubalis) from the vicinity of the city of Belem, Para State. Twenty three years later Silva et al. (1996) reported the occurrence of T. vivax in the north of Pantanal. The Pantanal is a seasonal floodplain of about 140, 000 km2. It is populated by 3, 996, 000 cattle and 4, 966 buffaloes. The Pantanal is one of the most important livestock regions of Brazil. The following year they reported outbreaks of T. vivax in the lowlands of Bolivia. With a population of 1, 598, 957 bovines, this is the most important livestock producing region of Bolivia.
The extended period between the report of Shaw & Lainson recording T. vivax, in the northern region of Brazil, and that of Silva et al. (1996), in the Pantanal, suggests that the Amazonian forest constituted a physical barrier impeding the moment of cattle between these regions. However, the 1970's experienced increased and accelerated activities in the construction of roads through the interior of the country and linking the north and the central regions. The roads, BR 163 and BR 230, link Cuiaba (Capital of Mato Grosso State and located 100 Km east of Poconé) to Belém, and have contributed to an increase in cattle throughout the region, this may have contributed to the spread of T. vivax in the Pantanal.
The increase in cattle trading between Brazil and Bolivia during the last year, due to depressed prices for Brazilian cattle, has caused an increase in the movement of horses and cattle between both countries. Around 180, 000 heads of Brazilian bovines were sold to Bolivia, particularly from the northern parts of Pantanal. The traditional cattle-raising system in the Pantanal is based on calf and yearling production. Its marketing involves animal transportation to market-places, river ports and railway stations. The most common method of transportation is on foot, herds averaging 906 animals and taking on average of 11 days to cover 230 km (Cadavid Garcia, 1985). Similar cattle-raising systems are used in the lowlands of Santa Cruz Department.
Conditions for the infection and transmission of T. vivax are greatest at the numerous resting places along the route, mainly near markets. The intermingling of animals from different locations in the proximity of potential hosts provides an excellent opportunity for disease transmission by the vectors. This could have contributed to the spread of the disease. Gardiner (1989) notes a temporal association between the rainy season, the abundance of biting flies, particularly Tabanidae, and an increase in prevalence of T. vivax infections in cattle. In the Santa Cruz Department, studies by Hall et al. (1993) on zoning the province into three regions of estimated tabanid fly challenge show that the Provinces of Velaco, Nuflo de Chavez, Guayaros and Chiquitos (lowlands) are in an area of high fly challenge. In the Pantanal, studies showed that the high vector season occurs in the first half of the rainy season, from September/October to December/January. However, the tabanids still remain in high numbers until the end of the rainy season. The rainy season represents the period of greatest risk of trypanosome transmission by these insects due to their abundance and the population peak of species of high vector potential, notably Tabanus importunus (Silva et al., 1995). Similar to Pantanal, in the lowlands of Santa Cruz Department, the rainy season could represent the period of major risk of trypanosome transmission by these insects. The results of this study suggest that the accelerated construction of roads through the interior of the country and the susequent linking, principally of the north and central west regions, contributed to the introduction of T. vivax into the Pantanal. Moreover, the increase in cattle trade between Brazil and Bolivia has been responsible for introduction of the parasite into the latter.
At the begining of November, 1996, several new cases of T. vivax were diagnosed in 50% (1/2) and 80.95% (17/21) of the cattle from Nabileque and Paiaguas subregions of Pantanal and Mato Grosso do Sul State. This last subregion is located at the border with Paraguay.
The disease symptons observed in Brazil and Bolivia were: fever, anemia, progressive weakness, loss of condition, loss of appetite, lethargy, weakness, substantial weight loss within a relative short period of time, anemia, progressive ematiation, abortion and death. The principal symptoms, in both countries, being substantial weight loss within a relative short period of time, anemia, abortion and death.
In a recent study (Dávila et al., 1997) measurements of T. vivax isolates from Brazil and Bolivia were compared. The difference in length among isolates from the Pantanal (18.73 um), Para (22.77 um) reported by Shaw and Lainson (1972) and Bolivia (15.86 um) were highly significant (p<0.001). Fairbaim (1953) showed that short forms were characteristic of the strain causing acute disease in cattle of West Africa, while long forms are associated chiefly with strains causing chronic infection in East Africa. As recent studies by RAPD (Random Amplified Polymorphic DNA) analysis showed that South American T. vivax originated from West Africa (Dirie et al., 1993), we believe that shorter forms reported in this work could be related with the acute disease observed by us and also observed in West Africa by Fairbairn (1953).
Current and recent historical evidence indicates that bovine trypanosomosis in the Pantanal, Brazil and lowland provinces of Santa Cruz Department, Bolivia has been a devastating disease, and that it is spreading to southwards through South America (Paraguay and Argentina). However, more studies will be necessary to determine the impact of the disease on the economy of the region.
Cadavid Garcia, E. A., 1985. Comercialização do gado bovino do Pantanal Mato-Grossense; município de Corumbá, MS. EMBRAPA/CPAP, Circular técnica 16. pp. 45.
Dávila, A. M. R., Ramirez, L. and Silva, R.A.M.S., 1997. Morphological and Biometrical Differences among Trypanosoma vivax Isolates from Brazil and Bolivia. Mem. Inst. Oswaldo Cruz, 92: (in press).
Dirie, M.F., Murphy, N.B. and Gardiner, P.R., 1993. DNA fingerprinting of Trypanosoma vivax isolates rapidly identifies intraspecific relationships. J Euk Mircrobiol, 40: 132-134.
Fairbaim, H., 1953. Studies on Trypanosoma vivax. IX. Morphological differences in strains and their relation to pathogenicity. Ann trop Med Parasit 47: 394-405.
Gardiner, P.R., 1989. Recent studies of the biology of Trypanosoma vivax. Advances in Parasitology, 28: 229-317.
Hall, M., Chainey, J., Betella, P. and Aramayo, J.L., 1993. Tabanidae of Santa Cruz Department, Bolivia, and Their Role as Pests of Livestock. October 1992 to March 1993. Final Report on ODA Animal Health Programme Project R5407. 66pp.
Leger, M. and Vienne, M., 1919. Epizootie a trypanosomes chez les bovines de la Guyane Françoise. Bull. Soc. Path. Exot, 12: 258-266.
Melendez, R.D,. Forlano, M., and Figueroa, W., 1995. Perinatal infection with Trypanosoma vivax in a calf in Venezuela. Trypnews, 2: 4.
Shaw, J.J. and Lainson, R., 1972. Trypanosoma vivax in Brazil. Annals of Tropical Medicine and Parasitology, 66: 25-32.
Silva, R.A.M.S., Barros, A.T.M; Herrera, H.M., 1995. Trypanosomosis outbreaks due to Trypanosoma evansi in the Pantanal, Brazil. A preliminary approach on risk factors. Revue Elev. Med. Vet Pays trop., 48: 315-319.
Silva, R.A.M.S., da Silva, J.A, Schneider, R.C., de Freitas, J., Mesquita, D.P., Mesquita, T.C., Ramirez, L., Davila, A.M.R., Pereira, M.E.B., 1996. Outbreak of Trypanosomiasis Due to Trypanosoma vivax (Ziemann, 1905) in Bovines of the Pantanal, Brazil. Mem. Inst. Oswaldo Cruz, Rio de Janeiro, 91: 561-562.
