key: cord-0005297-74vjx9xz authors: Ghirotti, M.; Semproni, G.; De Meneghi, D.; Mungaba, F. N.; Nannini, D.; Calzetta, G.; Paganico, G. title: Sero-prevalences of selected cattle diseases in the Kafue flats of Zambia date: 1991 journal: Vet Res Commun DOI: 10.1007/bf00497787 sha: a1c427587e4e8e1677fcc4246037c1ee0ddcbd66 doc_id: 5297 cord_uid: 74vjx9xz Sera from five traditionally managed herds grazing in the Kafue flats were tested for antibodies to bovine viral diarrhoea-mucosal disease (BVD-MD), parainfluenza 3 (PI3), infectious bovine rhinotracheitis-infectious pustular vulvovaginitis (IBR-IPV), bovine adenovirus 3 (BAV3) and Bluetongue (BT). The sero-prevalences of the first four diseases were respectively 76.2, 94.4, 42.1 and 87.4%. Five samples (2.3%) gave doubtful reactions for BT. Prevalences of 28.5% for brucellosis, 14% for Rift Valley fever (RFV), 0.9% for Q fever and 11.2% for chlamydiosis were also recorded. Significantly higher values for BVD-MD (p<0.005), IBR-IPV (p<0.01) and brucellosis (p<0.05) were found in animals over 1 year of age. No differences were recorded between herds or between male and female animals. The high concentration of wild and domestic ruminants grazing together in the flood plains during the dry season may be a major determinant of the high values observed. Traditional farmers, slaughterhouse workers and other people involved in livestock production are particularly at risk of contracting brucellosis and RVF because of the high prevalences in cattle and local habits favourable to their transmission. Cattle play an essential role in the agropastoral systems in Zambia. The national herd numbers over 2.5 million cattle while the human population is eight million (FAO-WHO-OIE, 1988) . About SO% of Zambia's cattle are in the traditional sector and the development potential of this sector is considerable. However, the offtake from traditionally managed herds is less than lo%, considerably lower than that from commercial farms (Perry et al., 1984) . In neighbouring countries, several viral diseases have been reported as causing loss of production in local herds, including bovine viral diarrhoea-mucosal disease (BVD-MD), parainfluenza 3 (P13) and infectious bovine rhinotracheitis-infectious pustular vulvovaginitis (IBR-IPV) (Provost et al., 1%7a,b; Taylor and Rampton, 1968; Jetteur et aI., 1988; Eyanga et al., 1989) . Furthermore, cattle can act as hosts for viruses which are pathogens for other domestic species, such as Bluetongue (BT) (Erasmus, 1975) . No information on such diseases in livestock is available from Zambia. Over 70% of the Zambian population is involved in agricultural activities, including animal husbandry (FAO, 1988) . Several zoonoses can be transmitted to personnel working in cattle production. Brucellosis, Rift Valley fever (RFV), Q fever and to a lesser extent bovine chlamydiosis, are of economic importance because they can also affect herd productivity through abortions, stillbirths and reduction in fertility and milk production. RVF may be responsible for severe signs often resulting in death. Human cases have generally followed outbreaks in livestock (Meegan, 1979) . In Zambia, epidemics of this infection in cattle were reported in Central and Southern Provinces during 1974 , 1978 and 1985 and seem to have been associated with human deaths (Hussein et al., 1987; Morita, 1988) . Serological studies on RVF in cattle gave conflicting results. While Hussein and colleagues (1987) reported over 50% of sera collected in Southern Province to be positive for RVF, Morita (1988) did not find any reactors in animals sampled from Mazabuka, although 11.4% of the tested resident human population had antibodies against the virus. Bovine brucellosis is particularly frequent in cattle in the Western Province of Zambia, which show about 30% positivity (d'cruz, 1976) . All the cattle there are under traditional management. Prevalences are also high in Southern and Central Provinces, where most of the national herd is found. On the southern bank of the Kafue river, d'Cruz (1976) recorded 14% reactors in Namwala (all these cattle being from the traditional sector), 4.4% in Mazabuka, 6.5% in Monze and 16.7% in Choma. In the last three districts a large proportion of livestock are bred in commercial farms. On the northern bank of the river, i.e. in Central Province, prevalences were 19.7% in Mumbwa (d'Cruz, 1976) and 10% in the Mukulaikwa area (Moorhouse and Snacken, 1983) . Data on Q fever and bovine chlamydiosis in livestock are not available from Zambia. However, these diseases have been reported in both people and cattle from neighbouring countries (Schutte et al., 1976; Gear et al., 1986) . One of the three major traditionally managed cattle populations of Zambia is to be found around the Kafue river plains, in Central and Southern Provinces. It is estimated to be about 700 000 head of cattle, approximately a quarter of the total national herd. These cattle and the Kafue river, a tributary of the Zambesi, are integral parts of a particular traditional farming system in which transhumance allows optimal utilization of the natural resources. A serological investigation into the prevalence of the major viral diseases and zoonotic infections was carried out in some of the traditionally managed herds grazing in the Kafue flats to obtain preliminary information on this particular cattle population and to provide recommendations for field staff involved in disease control. The location The Kafue flats are located at 15" 10' to 16" 1'S and 26" 2' to 28" 9'E, south-west of the capital city, Lusaka ( Figure 1 ). The elevation varies between 950 and 1050 metres above sea level, gradually declining towards the river. A few scattered hills are present in the plains. The vegetation is divided into three different belts. Moving away from the river they are (a) the floodplain zone itself with grass species adapted to periodical inundations, scarce thorny shrubs (Acacia albida) and palms (Borassus aethiopium); (b) the termitaria grassland, progressively covered with Euphorbia candelabra; and (c) the woodland savanna where most human settlements occur and Acacia, Albizzia, Combreturn and Termitalia are found. As in the rest of Zambia, the climate is characterized by three seasons: hot-dry from August to October, warm-wet from November to April and cool-dry from May to July. The peak of the rains occurs in December, the average annual precipitation being 800 mm. Rainfall patterns influence life in the flats since most of the plains are subject to periodical inundation from the river. After the peak floods in May, the subsiding waters leave valuable and abundant grassland. The lowest water levels are recorded in November. Integration of maize (formerly sorghum) and cattle production, the river levels and the farmers' seasonal activities and movements characterize the farming system in the Kafue flats. In November, as soon as the early rains come, oxen are used to plough maize fields. Until June, when the maize is ready, the cattle graze in the proximity of the village since there is abundant pasture and water. Once the crop is harvested and the grass becomes dry, they feed on maize by-products. When these sources are exhausted and water becomes scarce, often at the end of July, neighbouring herds link up and graze on the flats, where grass is abundant, sharing the pasture with wild ungulates. The cattle are driven back to their places of origin shortly before the return of the rains. Local cattle are of the Sanga type, Ila-Tonga breed. Herd size ranges between 20 and 100 head. Because of the importance of milk in the household diet, about one-third of the animals are breeding cows. Traditional farmers retain a similar proportion of working oxen since they provide draught power for farming activities. The lush plains sustain large numbers of different wild mammals. These are mainly concentrated in the three national parks situated along the Kafue river (Kafue, Lochinvar and Blue Lagoon). For example, it has been estimated that in Lochinvar alone there are about 42 000 Kafue Lechwe (Kobus leche kafuensis), the semi-aquatic antelope symbolic of these flood plains. The 214 sampled cattle belonged to live traditionally managed herds strategically located on the south-eastern bank of the Kafue river ( Figure 1 ). They were recorded as male or female calves (under one year of age), adult females, bulls or oxen, as shown in Table I . The calves in herd 5 were not sampled as they were very emaciated -Not sampled due to the prolonged dry season. All the sampled calves were over three months of age. The blood samples were collected using vacutainers in November and early December 1987, just before the onset of the rains. None of the cattle were vaccinated against the diseases tested for. All the herds were on the fringe of a 77zeileria pmvu infected area and they were therefore treated for ticks at weekly intervals during the rainy season. Sera were separated within 24 h of the blood being taken and stored at -30°C until tested. They were inactivated by heating at 56°C for 30 min before testing. Sera were tested against BVD-MD by a microserum neutralization technique. 100 TCID,, of a pretitred strain of BVD-MD, obtained from the National Animal Disease Laboratory, Ames, Iowa, USA, were added to serial doubling dilutions of the sera. After incubation at 37°C for 1 h, bovine testicular cells were added to each well to a concentration of 300,GOO cells per ml. The plates were then incubated at 37°C for 48 h in the presence of 4.5% CO, and for a further 5 h in the absence of CO, Neutralization or viral growth were assessed by microscopic examination. Haemagglutination-inhibition for PI3 and serum neutralization tests for IBR-IPV and bovine adenovirus 3 (BAV3) were carried out in microtitration plates according to standard techniques (MAFF/ADAS, 1984) . The strains of P13, IBR-IBV and BAV3 used were respectively SF4, R-63 and Weybridge. These three strains were all obtained from the Central Veterinary Laboratory, Weybridge, UK. The presence of BT antibodies was detected by an agar gel immunodiffusion test using the Onderstepoort BT strain. 4% noble agar was prepared in distilled water, then diluted with one volume of an alkaline buffer solution (pH 8.65). The plates were examined after 72 h. Standard techniques (Morgan, 1978) were used to detect Brucella abortus antibodies. Results were expressed as 0, 25, 50, 75 and 100% of positivity in the case of the Rose Bengal test (RBT), IU/ml for the serum agglutination test (SAT) and EEC U/ml for the complement fixation test (CFT). Titres greater than, or equal to, 25% for RBT, 13 III/ml for SAT and 22 EEC U/ml for CFT were considered as positive for brucellosis. Since none of the sampled animals was vaccinated against brucellosis, SAT was considered as the reference test and the results of this test were adopted for determining the sensitivity and specificity of the other two tests, i.e. RBT and CFT, in the diagnosis of bovine brucellosis under local conditions. To detect RVF antibodies, a haemagglutination-inhibition test was performed according to the method of Clarke and Casals (1958) using an RFV-inactivated antigen (Onderstepoort). Goose erythrocytes in phosphate buffer at a final pH of 6.0 were added to an antigen-serum mixture and incubated at 37°C. Titres greater than or equal to 1:20 were considered positive. The microcomplement fmtion test utilized for Q fever and chlamydiosis was as described by BaIdelli and colleagues (1975) . For chlamydiosis the antigen was strain A22 of ChZamydia ovis, kindly provided by the Moredun Institute, Edinburgh, while for Q fever it was a commercial product (Boehring-Werke). Threshold values for positivity were 1:16 for the former infection and 1:8 for the latter. Analysis of the data was carried out using the x2 test, or by Fisher's exact test when one of the expected values was less than 5, and a Mantel-Haenszel stratified analysis was carried out with the statistical package Epi Info (CDC-WHO, 1989). Table II summarizes the results of the tests. No significant differences in seroprevalence were found among herds or between male and female animals. On the other hand, adults gave significantly higher values for BVD-MD (p