RESUMO
The diagnosis of trypanosomosis in animals with low parasitaemia is hampered by low diagnostic sensitivity of traditional detection methods. An immunodiagnostic method based on a direct sandwich enzyme-linked immunosorbent assay (ELISA), using monoclonal antibodies, has been examined in a number of African laboratories for its suitability for monitoring tsetse control and eradication programmes. Generally, the direct sandwich ELISAs for the detection of trypanosomal antigens in serum samples have proved to be unsatisfactory with respect to diagnostic sensitivity when compared with traditional parasitological methods such as the dark ground/phase contrast buffy-coat technique. Consequently, antigen-detection systems exploiting various other direct, indirect and sandwich ELISA systems and sets of reagents are being developed to improve diagnosis. In addition, an existing indirect ELISA for the detection of antibodies has been improved and is being evaluated in the field in order to detect cattle that are or have been recently infected with trypanosomes. Developments and advantages of other diagnostic techniques, such as dip-stick assay and tests based on the polymerase chain reaction are also considered.
Assuntos
Tripanossomíase Africana/veterinária , Tripanossomíase Bovina/diagnóstico , Animais , Anticorpos Antiprotozoários/sangue , Antígenos de Protozoários/sangue , Bovinos , Ensaio de Imunoadsorção Enzimática/métodos , Sensibilidade e Especificidade , Trypanosoma congolense/imunologia , Trypanosoma vivax/imunologia , Tripanossomíase Africana/diagnósticoRESUMO
A case-control study of calves under 3 months of age was carried out by weekly visits to 15 farms in the canton of Tilarán, Costa Rica. Most farms were dedicated to beef or dual-purpose (DP) production. Faecal samples were collected over a 6-month period from a total of 194 calves with clinical signs and from 186 animals without clinical signs of diarrhoea as assessed by a scoring system. The samples were investigated for the presence of viruses, bacteria and parasites. Torovirus was detected for the first time in Costa Rica and was present in 14% of calves with diarrhoea and in 6% of the controls. Coronavirus and Rotavirus were less frequently encountered in either one of the groups (in 9 and 7% of scouring calves and in 1 and 2% of controls, respectively). Escherichia coli was detected in 94% of all the faecal samples, but isolates from only three samples from calves with diarrhoea contained the K99 antigen. Similarly, Salmonella was found only in scouring calves. Cryptosporidium oocysts were detected in animals with signs of diarrhoea, while other coccidia oocysts, Strongylida and Strongyloides eggs were frequently found in animals both with and without diarrhoea. A conditional logistic regression (CLR) analysis to compare healthy and scouring calves showed a significant difference with regard to the presence of Torovirus, Rotavirus and Coronavirus.
Assuntos
Doenças dos Bovinos/microbiologia , Diarreia/veterinária , Fezes/microbiologia , Animais , Estudos de Casos e Controles , Bovinos , Doenças dos Bovinos/epidemiologia , Doenças dos Bovinos/parasitologia , Coccídios/isolamento & purificação , Coronavirus/isolamento & purificação , Costa Rica/epidemiologia , Cryptosporidium/isolamento & purificação , Diarreia/microbiologia , Diarreia/parasitologia , Escherichia coli/isolamento & purificação , Fezes/parasitologia , Feminino , Modelos Logísticos , Masculino , Prevalência , Rotavirus/isolamento & purificação , Salmonella/isolamento & purificação , Strongyloides/isolamento & purificação , Torovirus/isolamento & purificação , Clima TropicalRESUMO
To determine the tick species hindering the cattle industry in Costa Rica and to assess infection rates of ticks with three important hemoparasite species, cattle were monitored during a period of six months (October 1992-March 1993). Four farms were located in the dry pacific region of the canton of Tilarán and a fifth farm on the slopes of the Poás volcano in a cool tropical cloud-forest ecosystem. On each farm 3 to 5 animals of 6 to 24 months of age were selected at random. All ticks were removed on a monthly basis from the right half side of each animal, while the site of attachment was recorded. Ticks were counted and differentiated according to species, developmental stage and sex. Moreover, engorged female ticks were assayed for the presence of Babesia bigemina, Babesia bovis and Anaplasma marginale using the polymerase chain reaction (PCR) multiplex system. Two species of ticks, Amblyomma cajennense and Boophilus microplus, were encountered on the cattle in the Tilarán region and one species, B. microplus, was detected in the Poás region. Two to ten times as many ticks were encountered in the Tilarán region than in the Poás region, which is in accordance with a stable enzootic protozoan disease situation in the former region and an unstable epizootic situation in the latter region. Nymphal and adult stages of both tick species were present in largest numbers on the ventral parts of the animals. PCR analysis of entire ticks indicated very high infection rates with hemoparasites of veterinary importance. This was in accordance with high seroprevalence rates in the hosts.
Assuntos
Doenças dos Bovinos/parasitologia , Infestações por Carrapato/veterinária , Carrapatos/fisiologia , Animais , Bovinos , Doenças dos Bovinos/epidemiologia , Costa Rica/epidemiologia , Feminino , Interações Hospedeiro-Parasita , Masculino , Reação em Cadeia da Polimerase/veterinária , Estações do Ano , Infestações por Carrapato/epidemiologiaRESUMO
To determine the tick species hindering the cattle industry in Costa Rica and to assess infection rates of ticks with three important hemoparasite species, cattle were monitored during a period of six months (October 1992-March 1993). Four farms were located in the dry pacific region of the canton of Tilar n and a fifth farm on the slopes of the Po s volcano in a cool tropical cloud-forest ecosystem. On each farm 3 to 5 animals of 6 to 24 months of age were selected at random. All ticks were removed on a monthly basis from the right half side of each animal, while the site of attachment was recorded. Ticks were counted and differentiated according to species, developmental stage and sex. Moreover, engorged female ticks were assayed for the presence of Babesia bigemina, Babesia bovis and Anaplasma marginale using the polymerase chain reaction (PCR) multiplex system. Two species of ticks, Amblyomma cajennense and Boophilus microplus, were encountered on the cattle in the Tilarán region and one species, B. microplus, was detected in the Poás region. Two to ten times as many ticks were encountered in the Tilarán region than in the Poás region, which is in accordance with a stable enzootic protozoan disease situation in the former region and an unstable epizootic situation in the latter region. Nymphal and adult stages of both tick species were present in largest numbers on the ventral parts of the animals. PCR analysis of entire ticks indicated very high infection rates with hemoparasites of veterinary importance. This was in accordance with high seroprevalence rates in the hosts
Assuntos
Animais , Masculino , Feminino , Bovinos , Doenças dos Bovinos/parasitologia , Infestações por Carrapato/veterinária , Carrapatos/fisiologia , Costa Rica , Doenças dos Bovinos/epidemiologia , Infestações por Carrapato/epidemiologia , Reação em Cadeia da Polimerase/veterinária , Interações Hospedeiro-Parasita , Estações do AnoRESUMO
Tsetse transmitted trypanosomiasis is possibly the major constraint on livestock and agriculture development in Subsaharan Africa. Control of the disease has been based on vector control as well as on the use of trypanocidal drugs to treat or prevent infection in animals. Both control methods are effective but have proven not to be sustainable. Moreover, the development of a vaccine against trypanosomiasis is unlikely to be successful in the near future. On the other hand, trypanotolerant cattle, like the N'Dama can survive and produce in tsetse affected areas without interventions. This taurine breed has been indigenous to Africa for approximately 7,000 years and forms presently about 6% of the bovine population of Africa. Generally the N'Dama are kept in the rural areas by the small-scale farmer as a multi-purpose animal. Recent studies have defined management characteristics and assessed the production potential at the village level and under ranching conditions of N'Dama cattle exposed to various levels of tsetse challenge. Furthermore, experimental infections showed conclusively the superior resistance to the effects of infection of the N'Dama cattle when compared to zebu cattle and have confirmed that trypanotolerance is innate in N'Dama cattle. Studies have been conducted on development of protective humoral and cellular responses, the regulation of parasite multiplication and control of anaemia. These studies provided tools for identifying components of trypanotolerance. The ability to resist the development of anaemia in the face of infection, has shown to be correlated with the capacity to be productive; moreover, PCV values can serve as selection criterium for trypanotolerance. Subsequently, repeatabilities and heritabilities of trypanotolerance and performance traits were estimated.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Animais Domésticos/imunologia , Insetos Vetores , Tripanossomíase Africana/veterinária , Tripanossomíase Bovina/imunologia , Moscas Tsé-Tsé , África , Criação de Animais Domésticos , Animais , Bovinos , Tolerância Imunológica , Tripanossomíase Africana/imunologiaRESUMO
Nine farms were each visited regularly for a year in 1979 and 1980 in Salta Province in the subtropics of Argentina. A necropsy was done at each visit and faecal and blood samples were taken from other animals mostly aged between 6 and 18 months. Ninety necropsies were done and nearly 1,500 faecal samples collected. Gastro-intestinal helminthiasis was most general and severe in autumn when calves were about 9 months old and this was followed by a dramatic fall in numbers of worms by the end of winter. Helminths were found in other organs but were not considered important. At peak periods 20% of the animals had worm egg counts of more than 750 epg and contained more than 1,000 Haemonchus worms. This species was considered to be the most important but other frequently encountered species were Oesophagostomum, Cooperia and Trichostrongylus spp. A list is given of all species found. Tracer calves were used to determine the periods of infestation. No hypobiosis was encountered. It was concluded that the sharp fall in numbers of worms after the autumn peak was due to the development of immunity by the majority of the young animals.
Assuntos
Doenças dos Bovinos/epidemiologia , Helmintíase Animal , Animais , Argentina , Bovinos , Fezes/parasitologia , Hemoncose/epidemiologia , Hemoncose/veterinária , Contagem de Ovos de Parasitas/veterinária , Estações do Ano , Clima TropicalRESUMO
Two thousand and ninety beef cattle livers from north-west Argentina were inspected at a large slaughterhouse in Salta; 13% were found to have lesions of fascioliasis and these were classified according to their severity. Of the livers condemned 182 (67.2%) were lightly affected, 77 (28.4%) moderately affected and only 12 (4.4%) severely affected. In a field survey 85 animals, mainly between 6 and 18 months old, were slaughtered and 12 (14%) had lesions of fascioliasis. The influence of Fasciola hepatica on weight gain in beef cattle was assessed on 2 farms. Infected animals were divided into 2 groups and I group was treated monthly. Only on 1 farm were the animals exposed continuously to infection. No differences in weight gain were found over 7 and 14 months respectively when compared to untreated controls. It was concluded that fascioliasis is widespread but at a low level in beef cattle.