John Bwalya Muma

Prevalence of antibodies to Brucella spp. and individual risk factors of infection in traditional cattle, goats and sheep reared in livestock-wildlife interface areas of Zambia.

A cross-sectional study was performed in the livestock–wildlife interface areas of Lochinvar and Blue Lagoon National Parks and the non-interface area of Kazungula to determine the prevalence of antibodies to Brucella spp. in domestic ruminants and identify individual animal risk factors of infection. A total of 1245 cattle from 124 herds and 280 goats and sheep from 29 flocks were tested sequentially for Brucella antibodies using the Rose Bengal test (RBT) and competitive ELISA. In cattle, individual seroprevalence ranged from 14.1% to 28.1%, while herd sero–prevalence ranged from 46.2% to 74.0% in the three study areas. No goat or sheep tested positive for Brucella antibodies. Three types of cattle grazing strategies were encountered: locally grazed herds (LGH), transhumantly grazed herds (TGH) and river flood plain grazed herds (FGH). Brucella seroprevalence was seen to vary according to area and grazing strategy: Lochinvar and transhumant grazed herds recorded the highest figures, respectively. Age, sex and history of abortion were found to have independent effects on individual seroprevalence. This study establishes that brucellosis is endemic in domestic animals in the livestock–wildlife interface areas of Blue Lagoon and Lochinvar national parks and the disease is also present in Kazungula. We observed that type of grazing strategy had significant impact on cattle Brucella seroprevalence and that transhumant herds were at high risk of being infected.

Prevalence of bovine tuberculosis and animal level risk factors for indigenous cattle under different grazing strategies in the livestock/wildlife interface areas of Zambia.

A cross-sectional study was conducted to investigate the prevalence and animal level risk factors for bovine tuberculosis (BTB) in indigenous cattle of the livestock/wildlife interface areas in Zambia. A total of 944 cattle from 111 herds were investigated. The comparative intradermal tuberculin test (CIDT) was used to identify reactor animals for BTB. Animal level data on sex, age, parity and body condition score were registered. The overall animal prevalence of BTB as determined by the CIDT was 6.8% (95% CI: 4.2, 9.5%). In Lochinvar and Blue Lagoon areas, animal level prevalence were observed at 5.2% (95% CI: 2.2, 8.2%) and 9.6% (95% CI: 6.1, 13.2%), respectively. Kazungula, an area outside the livestock/wildlife interface, had a prevalence of only 0.8% (95% CI: 0.0, 2.3%). The age of the animal, its body condition score and the type of management system, were predictive of its BTB status. The study revealed that BTB was relatively high in the livestock/wildlife interface areas of Lochinvar and Blue Lagoon compared to Kazungula. These findings should raise a serious public health concern considering the extent to which the communities of the study areas are in contact with their animals and the levels at which they use untreated milk.

Risk factors associated with bovine tuberculosis in traditional cattle of the livestock/wildlife interface areas in the Kafue basin of Zambia.

We conducted a cross-sectional study from August 2003 to February 2004 to identify risk factors for bovine tuberculosis (BTB) in the Kafue basin of Zambia. We investigated a total of 106 herds of cattle for presence of BTB using the comparative intradermal tuberculin test (CITT) while an interviewer-administered questionnaire was used to gather epidemiological data on herd structure, management and grazing strategies. BTB prevalence at herd level was estimated and possible risk factors were investigated using the multiple logistic regression model. The true herd level prevalence of BTB was estimated at 49.8% (95% CI: 37.9, 61.7%). The logistic regression model showed that cattle herd BTB status was highly associated with area and husbandry practices. When compared to Kazungula, cattle herds in Blue Lagoon were more likely to test positive for BTB when other factors such as management practices were controlled (OR=10.5). In terms of grazing strategies, transhumant herds (TH) had higher odds (OR=3.0) of being positive compared to sedentary herds (OR=1.0). The results in this study provide preliminary information about potential risk factors that were found to be associated with BTB status in cattle.

Herd-level factors for Brucella seropositivity in cattle reared in smallholder dairy farms of Zimbabwe.

A cross-sectional study was conducted to investigate factors for Brucella seropositivity in smallholder dairy cattle herds from Gokwe, Marirangwe, Mushagashe, Nharira, Rusitu and Wedza areas located in different agro-ecological regions of Zimbabwe between September 2004 and November 2005. Sera were collected from cattle aged > or = 2 years from 203 herds. Data on herd-level and management variables were collected using a structured questionnaire. Sera were screened for anti-Brucella antibodies using the Rose Bengal test (RBT) and confirmed by competitive ELISA (c-ELISA). A herd was classified as Brucella seropositive if at least one animal tested seropositive on both tests. The herd-level factors for Brucella seropositivity were tested using multivariable logistic model with herd infection status as dependent variable while the levels of exposure in individual animals within-herds were analysed by negative binomial regression using the number of positive animals as the outcome. Of the 203 herds tested, 52 (25; 95% CI: 18.1, 31.9%) tested seropositive for brucellosis. Using the logistic regression model we identified area, with both Rusitu (OR=0.26; 95% CI: 0.07, 1.03) and Wedza (OR=0.07; 95% CI: 0.01, 0.49) having lower Brucella seropositivity compared to Gokwe. Keeping mixed cattle breeds (OR=8.33; 95% CI: 2.70, 25.72) compared to single breed herds, was associated with increased herd seropositivity. The farmers knowledge of brucellosis was associated with lower odds (OR=0.17; 95% CI: 0.05, 0.55) of farms testing seropositive. The odds of Brucella seropositivity were progressively higher with increasing stocking density and herd size. Using the negative binomial regression model we identified area, keeping mixed breed herds, stocking density and herd size as independently associated with increased counts of seropositive cattle in a herd.

Bayesian modelling to estimate the test characteristics of coprology, coproantigen ELISA and a novel real-time PCR for the diagnosis of taeniasis.

To estimate and compare the performances of coprology, copro‐Ag ELISA and real‐time polymerase chain reaction assay (copro‐PCR) for detection of Taenia solium tapeworm carriers.

The incidence of human cysticercosis in a rural community of Eastern Zambia

A community-based longitudinal study was performed in the Eastern Province of Zambia, in which repeated serological samplings were done to determine the incidence of human cysticercosis. Three sampling rounds were carried out at six months intervals. A total of 867 participants presented for all three samplings. All samples were tested for the presence of cysticercus antigens using a monoclonal antibody-based enzyme-linked immunosorbent assay (sero-Ag-ELISA), while a randomly selected sub-sample of 161 samples from each sampling round was tested for specific antibodies using a commercial enzyme-linked immunoelectrotransfer blot (EITB) assay. Stool samples (n = 226) were also collected during the final round of sampling for taeniosis diagnosis by coprology and coproantigen ELISA. Cysticercosis seroprevalence varied from 12.2% to 14.5% (sero-Ag) and from 33.5% to 38.5% (sero-Ab) during the study period. A taeniosis prevalence of 11.9% was determined. Incidence rates of 6300 (sero-Ag, per 100000 persons-year) and 23600 (sero-Ab, per 100000 persons-year) were determined. Seroreversion rates of 44% for sero-Ag and 38.7% for sero-Ab were recorded over the whole period. In conclusion, this study has shown the dynamic nature of T. solium infections; many of the people at risk become (re)infected due to the high environmental contamination, with a high number turning seronegative within a year after infection. An important number of infections probably never fully establish, leading to transient antibody responses and short-term antigen presence.

Responses to tuberculin among Zebu cattle in the transhumance regions of Karamoja and Nakasongola district of Uganda

Responses to tuberculin in Zebu cattle of the transhumant pastoral farming system in Karamoja region and Nakasongola district in the north-eastern and mid-central regions in Uganda, respectively, were investigated using a comparative intradermal tuberculin skin test. Of the 1864 cattle tested from 30 large units (superherds) in Karamoja and 7 herds in Nakasongola, a total of 28 animals from 19 herds (51.4%) tested positive. Inter-district tuberculin reactor prevalence variations seemed to be influenced by climate, with impact on both the management patterns and transmissibility of agent. High herd tuberculin reactor prevalence (51.4%) was attributed to widespread contacts and mixing of animals between herds. Low individual animal tuberculin test positivity (mean = 1.4%) was attributed to low transmissibility of the agent under the Karamoja climate, which is semi-arid, and to increased resistance due to non-specific response to environmental mycobacteria and natural selection, since there was no active control against bovine tuberculosis. Owing to similarities in management practices in Karamoja and widespread risk factors, it was difficult to identify which were more important, but variations in sources of drinking water pointed to provision of lake and borehole water during dry season as reducing the risk. Positive bovine tuberculin reactor prevalence and skin reactor status were related to age.

Risk factors for Brucella spp. infection in smallholder household herds.

Risk factors for Brucella infection, the association and impact of Brucella seropositivity on abortions were investigated in cattle (n=1291) reared in smallholder household herds (n=203) from six geographical areas of Zimbabwe between September 2004 and 2005. Data on management, abortion and herd structure were collected. Sera were tested for Brucella antibodies using the Rose Bengal test and a competitive enzyme-linked immunosorbent assay. Data were analysed by generalized estimating equation and logistic regression models. Brucella antibodies were estimated at 5·5% and 22·9% for individual cattle and herds, respectively. Abortions were reported in 3·2% of cows and 22·0% herds. The age of cows and Brucella seropositivity predicted abortion. For herds, Brucella seropositivity, geographical area, purchase of cattle and large herd size were independently associated with increased odds of abortion. Exposure to Brucella had a significant impact on abortion. These results highlight the important risk factors for Brucella spp. infection in smallholder herds. Thus, brucellosis control programmes which take these factors into consideration will be beneficial.

Isolation and characterization of Mycobacterium bovis strains from indigenous Zambian cattle using Spacer oligonucleotide typing technique

BackgroundBovine tuberculosis (BTB), caused by Mycobacterium bovis, has remained a major source of concern to public health officials in Zambia. Previous investigations have used traditional epidemiological methods that are unable to identify the causative agent and from which dynamics of disease dispersion is difficult to discern. The objective of this study was to isolate, characterize and determine the genetic diversity and relatedness of M. bovis from major cattle rearing districts in Zambia by spoligotyping. A total of 695 carcasses were examined and 98 tissues had gross post-mortem lesions compatible with BTB.ResultsForty-two out of the ninety-eight suspected tissues examined had culture properties characteristic of mycobacteria from which 31 isolates yielded interpretable spoligotypes. This technique showed good discriminatory power (HGDI = 0.98), revealing 10 different spoligotype patterns. Twenty-seven isolates belonged to one cluster with more than 95% similarity and inside the cluster, one predominant spoligotype was found in 20 (64.5%) of the isolates tested. The highest number of spoligotypes was observed among samples from Namwala district. Spoligotypes from 26 (83.9%) of the isolates belonged to five spoligotypes that have been reported before while the remaining 5 (16.1%) isolates had unique spoligotypes that are being reported for the first time; these have been assigned numbers SB1763 to SB1767. Five of the 6 districts had the predominant spoligotype (SB0120).ConclusionThe study has described the dispersion patterns of M. bovis in Zambian cattle for the first time and has identified 5 spoligotype patterns specific to Zambia. The observation of an overlap in the spoligotype pattern SB0120 in 5 of the 6 districts suggests the probability of sharing a common source of infection.

Tuberculosis in Kafue lechwe antelopes (Kobus leche Kafuensis) of the Kafue Basin in Zambia.

Tuberculosis (TB) has been reported in the Kafue lechwe antelopes (Kobus leche Kafuensis) of Zambia. However, previous reports are restricted to the southern parts in Lochinvar, where only old male animals were investigated. This study was conducted to gather epidemiological information on TB in Lechwe antelopes across sexes and age groups in relation to other explanatory variables of disease occurrence in the Kafue Basin. Animals were hunted under a special licence to investigate diseases in the Kafue Basin during the 2004, 2005 and 2008 hunting seasons. Histopathology, acid-fast staining and mycobacterial culturing from tissue samples were conducted. A total of 119 animals were slaughtered with an estimated age range of 2.5-20 years. Of these, 29 (24.3% [95% CI: 16.5, 32.3%]) had necropsy lesions suggestive of tuberculosis, of which 21 (17.6% [95% CI: 10.7, 24.6%]) tested positive on acid-fast staining while 33 (27.7% [95% CI: 19.6, 35.9%]) showed culture and colony morphological characteristics suggestive of Mycobacterium species. On univariate analysis, animals with poor body condition were twice as likely to have tuberculosis associated lesions as those having good body conditions (OR=2.3, 95% CI: 0.6, 9.3%). Based on lesion distribution, a respiratory route of mycobacterial infection is intimated.