疑似肉牛传染性胸膜肺炎防治研究

近年来,有肉牛发生一种顽固性呼吸道病,以高热、咳嗽、气喘、病死率高为特征,给养殖户造成一定经济损失,为了解决这一问题,笔者对疑似传染性胸膜肺炎病牛采用流行病学调查、临床症状、病理剖检、实验室诊断等方法进行系统研究,以期尽早控制该病。     

Within-herd spread of contagious bovine pleuropneumonia in Ethiopian highlands

Contagious bovine pleuropneumonia (CBPP) is a major threat for cattle health and production in Africa. This disease is caused by the small-colony type of Mycoplasma mycoides subspecies mycoides (MmmSC). Transmission occurs from direct and repeated contacts between sick and healthy animals. Veterinary services recently reported a resurgence of CBPP in the province of West Wellega, in the Ethiopian highlands. A research program was set up to estimate the epidemiological parameters of the within-herd infection spread. A follow-up survey was implemented in 71 sampled herds of the Boji district (West Wellega province). Fifteen herds were classified as newly infected and used in a serological- and clinical-incidence study. The overall 16-month cumulative sero-incidence risk was 34%. Clinical cases were recorded for 39% of the seropositive cattle; case-fatality risk was 13%. There was no evidence of benefit on infection spread of CBPP-control measures used locally by farmers (isolation or antibiotic treatments of sick animals). This might be related to a lack of power in the statistical analyses or to a quality problem for the medications used (and more generally, for health-care delivery in the Boji district).     

Challenges of controlling contagious bovine pleuropneumonia in sub-Saharan Africa

Contagious bovine pleuropneumonia (CBPP) is a disease of economic importance that is widely distributed in sub-Saharan African and contributes significantly to cattle morbidity and mortality. Control of CBPP offers a number of challenges as a result many developing countries in Africa are still struggling with this disease. In this study, we look at the challenges encountered in CBPP control in sub-Saharan Africa from the Zambian perspective. In conducting this study, we reviewed scientific literature and reports from the Ministry of Agriculture and Livestock and related animal institutions, and also made interviews with experts and key government officials involved in CBPP control in Zambia. Among the challenges identified for the successful control of CBPP were as follows: failure in the delivery of veterinary services, lack of a cattle identification system, natural phenomenon, livestock husbandry systems in the traditional sector, human movements, traditional practices among cattle farmers and cattle marketing systems. It was seen that the epidemiology of CBPP in Zambia is influenced by both ecological and anthological factors. Therefore, design and implementation of any control or eradication programme should be area/regional-dependent taking into account the different factors influencing disease transmission and maintenance.     

Abattoir-based survey of contagious bovine pleuropneumonia in cattle in Turkey

Blood samples collected from 945 cattle at four local abattoirs in Turkey were examined for contagious bovine pleuropneumonia (CBPP) by the complement fixation test (CFT) and competitive ELISA (cELISA). In addition, the carcases of the animals were examined macroscopically at the abattoirs and 62 lung samples which had lesions suggestive of CBPP were collected for bacteriological culture. To identify suspicious isolates the PCR was used in addition to the routine biochemical tests. By the CFT, two of the 945 serum samples were seropositive, and by the cELISA, four of them were seropositive. In the bacteriological culture of the lungs, growth was observed in 18 (29 per cent) of the samples by the observation of turbidity in the broths. However, when these broths were inoculated into an agar base, growth was observed in only three (4.8 per cent) samples. These isolates were identified as Mycoplasma species on the basis of biochemical tests. In the PCR analysis of DNA extracted from the broths, none of the isolates was identified as Mycoplasma mycoides subspecies mycoides small colony or one of the members of the M mycoides cluster, but amplification was obtained in only eight (44.4 per cent) of 18 samples, using Mycoplasma-genus specific primers. These DNA samples were examined further with primers specific to 16S rRNA and were then sequenced and compared with the databanks; DNA homologies at different levels were observed in five samples, with Mycoplasma alkalescens, Mycoplasma canadense, Mycoplasma bovis and Mycoplasma bovigenitalium.     

Indirect infection of cattle with contagious bovine pleuropneumonia.

Hay infected with Mycoplasma mycoides sub-species mycoides (M mycoides) was fed to six animals on three occasions. Five animals developed complement-fixing antibody in their sera and gave a positive reaction to the comparative intradermal allergic test. No animal died from contagious bovine pleuropneumonia (CBPP) but when they were killed, three had unequivocal lesions of the disease. M mycoides was isolated from the animals with these lesions but not from the others. CBPP was transmitted to two animals put in contact with those animals showing disease, and M mycoides was recovered from lesions in both animals. It is suggested that when unexplained outbreaks of CBPP occur, the possibility of indirect transmission should be considered.     

Some evidence of an age susceptibility to contagious bovine pleuropneumonia

In two separate experiments it was shown that cattle over three years of age were more resistant to contagious bovine pleuropneumonia (CBPP) than younger animals. A statistical analysis of the results of one of the trials indicated that the difference in the response to challenge between calves less than one year old and animals between two and three years old was not significant. However, when these two groups were compared with animals over three years old the results were highly significant (P less than 0.001). When death was used as the sole criterion of response to challenge a similar picture was seen: nine 14 calves died, four of 15 animals aged between one and two years died, five of 11 animals aged between two and three years died, none of 16 animals aged over three years died. No attempt is made to explain this increase in resistance with increasing age. It is suggested that a better knowledge of the factors that influence resistance and susceptibility would be of value in understanding the pathogenesis of CBPP. It is recommended that to ensure maximum susceptibility of control animals in vaccine trials, all animals used should be less than three years old.     

A model of contagious bovine pleuropneumonia transmission dynamics in East Africa

The dynamics of contagious bovine pleuropneumonia (CBPP) transmission vary widely between livestock production systems. This paper describes the development of a homogeneous, stochastic, compartmental model for CBPP transmission in pastoral herds of East Africa. The model was built using parameter estimates based on data published in the literature and on observations of livestock owners obtained through participatory research. The basic reproduction number for CBPP in southern Sudan was estimated to range from 3.2 to 4.6. The homogeneous model indicates that the critical community size for the persistence of CBPP falls within the typical herd sizes for pastoral communities in East Africa suggesting that individual isolated herds are capable of maintaining infection indefinitely. Vaccination alone with currently available vaccines was unlikely to eradicate the disease.     

Prevalence of contagious bovine pleuropneumonia (CBPP) in northern Nigeria

An abattoir study on the prevalence of contagious bovine pleuropneumonia (CBPP) in five cattle-producing states of Nigeria from 1988 to 1997 was carried out. A total of 1,936,015 slaughtered cattle was examined for characteristic CBPP lung lesions. The overall lesion-based prevalence of CBPP was 0.29% (95% CI 0.24, 0.35). The prevalence varied significantly (P<0.05) by state but not across the years. A total of 279 CBPP outbreaks occurred and overall vaccination coverage was only 9.7%, both varied over the years and across the states. The reasons for inadequate vaccination coverage for CBPP as well as the need for re-establishment of a national CBPP control programme are suggested.     

Experimences with a lyophilised contagious bovine pleuropneumonia vaccine in the ivory coast

Summary Trials on a lyophilised vaccine prepared fromM. mycoides var.mycoides strain T1, were carried out on humpless N'dama and Baoulé cattle and on zebu cattle. Post-vaccinal complications in some animals made the vaccine unsuitable under prevailing conditions for widespread field use on the humpless cattle in Ivory Coast. However the post-vaccinal lesions can be controlled and the proven immunological effectiveness of this lyophilised product have convinced the author that its use should be gradually extended as staff training and improved facilities permit. The product was acceptable for field vaccination of the zebu herds. The number and extent of local lesions were much reduced in herds revaccinated after one year. Serological findings based on the complement fixation test are discussed.

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Sumario Se realizaron vacunaciónes con una vacuna preparada deM. mycoides var.mycoides cepa T1, en ganado bovino N'dama sin joroba, ganado Baoulé y en ganado cebú. Las complicaciones post-vaccinales en algunos animales hizo que la vacuna no sea la adecuada considerando las condiciones prevalentes para su uso en el campo en el ganado sin joroba ne la Costa de Marfil. Sin embargo, las lesions post-vacunales pueden ser controladas y la probada efectividad inmunológica de este producto liofilizado han convencido al autor de que su uso debería de extenderse gradualmente tanto como el adiestramiento del personal y la mejora de facilidales lo permitan. El producto fue aceptable para la vacunación de campo del ganado cebú. El número y extensión de las lesions locales fue mucho mas reducido en hatos revacunados despues de un a?o. Se discuten hallazgos serológicos basados en la prueba de fijación de complemento.

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Résumé Des essais avec un vaccin lyophilisé préparé avec la souche T1 deM. myco?des var.myco?des ont été effectués sur du bétail zébu et sur du bétail sans bosse des races N'dama et Baoulé. Des réactions post-vaccinales observées chez certains animaux font que ce vaccin n'est pas recommandable pour son emploi à large échelle chez le bétail taurin de la C?te d'Ivoire dans les circonstances actuelles. Cependant ces complications vaccinales peuvent être combattues et l'efficacité immunologique indubitable de ce vaccin lyophilisé a convaincu l'auteur que son emploi devrait être progressivement étendu dans la mesure oú l'entra?nement du personnel et des facilités améliorées le permettraient. Ce vaccin est satisfaisant pour la vaccination de masse dans les troupeaux de zébus. Le nombre et l'importance des réactions locales sont réduites de beaucoup chez les animaux revaccinés après un an. Des données sérologiques obtenues par la méthode de fixation du complément sont discutées.

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Serving on a United Nations Development Programme/Technical Assistance assignment on the control of contagious bovine pleuropneumonia with the Ministry of Animal Production, Republic of the Ivory Coast