Bacterial and Fungal Diseases
A total of 79 scientific articles related to bacterial and fungal diseases have been published to date. However, only one article has so far been published on fungal diseases (zygomycosis and aspergillosis in breeder layer cockerels). Of the 78 publications on bacterial diseases, 55.1% (43/78) focused on bacterial zoonoses. Bacterial zoonoses researched on include anthrax, bartonellosis (cat scratch disease due to Bartonella henselae), brucellosis, leptospirosis, Q fever, salmonellosis, tuberculosis and yersiniosis (plague).
The practical research conducted by the Faculty addresses some very important aspects aimed at understanding bacterial zoonoses, their identification, their prevalence and risk factors; which ultimately contribute to designing effective disease control. The Faculty has focused its research on key bacterial zoonoses such as brucellosis, anthrax, tuberculosis and leptospirosis which are all of public health significance.
Spatio-temporal studies of anthrax made it possible to identify high risk areas and seasonal trends; enabling development of contingency plans for different risk locations, better resource allocation and improved preparedness in the event of an outbreak. The spatial model tested improved the understanding of anthrax ecology and can be potentially used in devising better control strategies of the disease in the country. Anthrax awareness studies elucidated important risk factors contributing to frequent human anthrax outbreaks in Zimbabwe thereby indicating possible intervention strategies. Bacillus anthracis soil isolation studies showed that there are areas contaminated with viable B. anthracis spores for at least 12 months after the last outbreak; indicating that decontamination of affected areas may help reduce animal and human anthrax incidence. A temperature-time combination of 75oC for 15 minutes was shown to be optimum for soil isolation with PCR targeting virulence plasmids providing a rapid confirmation of B. anthracis.
Over 50% of the work on zoonoses has focused on brucellosis. Bovine brucellosis is a disease of both economic and zoonotic importance worldwide, especially in sub-Saharan Africa. Research by the Faculty has greatly contributed to surveillance, identification of risk factors and suggesting control measures against brucellosis among domestic ruminants in both commercial and smallholder farms. The work has further contributed to characterization of Brucella species affecting domestic ruminants in Zimbabwe. Furthermore, it has contributed to the evaluation of several serological tests, promoting the use of techniques with high sensitivity and specificity in disease surveillance and control programs in commercial and smallholder farms. In turn, the ultimate effect is the significant reduction in the public health risks associated with the disease in cattle.
Research on bartonellosis provided evidence showing domestic cats to be the principal reservoirs of B. henselae, the aetiological agent of human diseases that include cat-scratch disease, bacillary angiomatosis, bacillary peliosis and a febrile bacteraemia syndrome. In addition, serological evidence ofbartonellosiswas shown in dogs from widely separated communal lands in Zimbabwe. These results have implications for human health, particularly pet owners and animal handlers.
Results on Q fever studies indicate that cats in Zimbabwe are infected with C. burnetii and should be considered as sources of infection for humans. In other domestic animals, serological evidence of Q fever infection was found in 39% of cattle (n = 180), but only 15% of dogs (n = 27) and 10% of goats (n = 180). The results suggest that cattle are important reservoirs of C. burnetii in Zimbabwe. Furthermore, the serological evidence of Q fever infection was found in 37% of humans (n = 494). Findings of these studies alert health workers to this infection, which apparently occurs frequently in Zimbabwe even though clinical cases have not been reported.
Healthy farmed Nile crocodiles (Crocodylus niloticus) in Zimbabwe were found harbouringSalmonella spp in their intestines and salmonellae have been isolated from meat samples of slaughtered crocodiles. These observations indicate that there is potential danger to humans arising from the trade in and consumption of crocodile meat. Implementation of measures to control and minimize Salmonella’s contamination of crocodile meat needs serious and careful considerations. Recent salmonellosis studies in poultry provided evidence of S. Enteritidis infection. The identification of multi-drug-resistant S. Enteritidis is of public health concern. Stringent control of S. Enteritidis and proper monitoring of antimicrobial usage in chicken farms will reduce the public health risk of human salmonellosis.
Recent work on bovine tuberculosis (bTB) confirmed for the first time the presence of Mycobacterium bovis in Gonarezhou National Park (GNP) buffaloes. The presence of bTB in wildlife has implications for the conservation of the wildlife species affected and the health of humans and livestock living at the wildlife–livestock–human interface. Development and implementation of adequate risk-mitigation strategies should be done to reduce the risk for bTB transmission to livestock and humans living at the periphery of the unfenced Gonarezhou National Park.
Four common rodent species (Mastomys natalensis, Rattus rattus, Rhabdomys pumilio&Tatera leucogaster) were found to be hosts of human plague vectors; Xenopsylla brasiliensis, Dinopsyllus lypusus and Ctenophthalmus calceatus. Findings of the studies support the reported pattern of plague outbreaks occurrence in the country. Environmental management and chemical control measures should be taken particularly in the informal settlements where risk of plague outbreaks appearsto be high. The results also showed that periurban cultivation should be discouraged to prevent wild, peridomestic, and domestic rodent interactions.