A Review of Bovine Tuberculosis in the Kafue Basin Ecosystem

The Kafue basin ecosystem is the only remaining natural habitat for the endangered Kafue lechwe antelope (Kobus leche Kafuensis). However, hydroelectricity power production, large-scale sugar plantations, commercial fishing and increasing livestock production are threatening its natural existence and sustainability. Further, increasing human settlements within and around the Kafue basin have resulted in decreased grazing grounds for the Kafue lechwe antelopes despite a corresponding increase in cattle population sharing the same pasture. Baseline epidemiological data have persistently reported findings of bovine tuberculosis (BTB) in both wild and domestic animals, although these have been deficient in terms of describing direct evidence in the role of either lechwe antelopes or cattle in the reported observations. Despite the current literature being deficient in establishing the casual role and transmission patterns of BTB, a bimodal route of infection at the livestock/wildlife interface has been postulated. Likewise, it is not known how much of (BTB) has the potential of causing disease in humans. This paper, seeks to underline those aspects that need further research and update available data on BTB in the Kafue basin with regards to the prevalence, distribution, risk factors, threats on wildlife conservation, livestock production, public health implications, and possible mitigatory measures

A Review of Ecological Factors Associated with the Epidemiology of Wildlife Trypanosomiasis in the Luangwa and Zambezi Valley Ecosystems of Zambia

Trypanosomiasis has been endemic in wildlife in Zambia for more than a century. The disease has been associated with neurological disorders in humans. Current conservation strategies by the Zambian government of turning all game reserves into state-protected National Parks (NPs) and game management areas (GMAs) have led to the expansion of the wildlife and tsetse population in the Luangwa and Zambezi valley ecosystem. This ecological niche lies in the common tsetse fly belt that harbors the highest tsetse population density in Southern Africa. Ecological factors such as climate, vegetation and rainfall found in this niche allow for a favorable interplay between wild reservoir hosts and vector tsetse flies. These ecological factors that influence the survival of a wide range of wildlife species provide adequate habitat for tsetse flies thereby supporting the coexistence of disease reservoir hosts and vector tsetse flies leading to prolonged persistence of trypanosomiasis in the area. On the other hand, increase in anthropogenic activities poses a significant threat of reducing the tsetse and wildlife habitat in the area. Herein, we demonstrate that while conservation of wildlife and biodiversity is an important preservation strategy of natural resources, it could serve as a long-term reservoir of wildlife trypanosomiasis

Detection of Parasites and Parasitic Infections of Free-Ranging Wildlife on a Game Ranch in Zambia: A Challenge for Disease Control

Ex-situ conservancies are expanding alternatives to livestock production in Zambia albeit the lack of information on circulating infectious parasites from wildlife. Therefore, 12 wildlife species were examined on a game ranch were all species were found to be infected by Rhipecephalus spp. Haemoparasite infections were estimated at 7.37% (n = 95) with Babesia spp. detected in bushbuck (Tragelaphus scriptus); Anaplasma marginale in impala (Aepyceros melampus) and puku (Kobus vardonii) for the first time in Zambia. The majority of worm species isolated from bovids were not detected in equids and, vice versa. Our findings intimate ecological and behavioural patterns of some animals as deterministic to exposure. Kafue lechwe (Kobus leche kafuensis) had the widest range of worm species with more infected organs than other animals suggesting their semi aquatic nature contributory to prolonged worm exposure compared to other animals. On the other hand, Kafue lechwe had the least tick infections attributable more to shorter attachment periods as they spend prolonged periods submerged in water. Our findings indicate the vital role that wildlife plays in the epidemiology of parasitic diseases. To reduce the infection burden, control measures should be focused on reducing transmission to highly susceptible animal species as described herein

Antigen dose and humoral immune response correspond with protection for inactivated infectious pancreatic necrosis virus vaccines in Atlantic salmon (Salmo salar L)

An enduring challenge in the vaccinology of infectious pancreatic necrosis virus (IPNV) is the lack of correlation between neutralizing antibodies and protection against mortality. To better understand the immunological basis of vaccine protection, an efficacy trial including Atlantic salmon (Salmo salar L.) vaccinated with a high antigen (HiAg) or low antigen (LoAg) dose vaccine was carried out in a cohabitation challenge model using the highly virulent Norwegian Sp strain NVI015. To pinpoint the immunological basis of vaccine protection, pathogenic mechanisms of IPNV were unraveled in control fish while obtaining feedback on mechanisms of protection in the vaccinated fish. During the incubation period, infection rates were highest in control fish, followed by the LoAg group with the lowest infections being in the HiAg group. Although both the liver and pancreas are target organs prone to tissue damage, infection in the liver was delayed until acute infection in most fish. A correlate of pathology determined as the cutoff threshold of viral copy numbers linked to tissue damage in target organs was estimated at ≥ 107.0, which corresponded with an increase in mortality. The kinetics of IFNα and Mx expression suggests that these genes can be used as biomarkers of IPNV infection progression. Mechanisms of vaccine protection involved reducing infection rates, preventing infection of the liver and reducing virus replication in target organs to levels below the correlate of pathology. Overall, the study shows that antigen dose corresponds with vaccine efficacy and that antibody levels can be used as a signature of protective immunity against pathological disease and mortality

Characterization of virulence and antimicrobial resistance genes of Aeromonas media strain SD/21–15 from marine sediments in comparison with other Aeromonas spp.

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Comparative Intradermal Tuberculin Testing of Free-Ranging African Buffaloes (Syncerus caffer) Captured for Ex Situ Conservation in the Kafue Basin Ecosystem in Zambia

Bovine tuberculosis (BTB) is endemic in African buffaloes (Syncerus caffer) in some National Parks in Southern Africa, whilst no studies have been conducted on BTB on buffalo populations in Zambia. The increased demand for ecotourism and conservation of the African buffalo on private owned game ranches has prompted the Zambian Wildlife Authority (ZAWA) and private sector in Zambia to generate a herd of “BTB-free buffaloes” for ex situ conservation. In the present study, 86 African buffaloes from four different herds comprising a total of 530 animals were investigated for the presence of BTB for the purpose of generating “BTB free” buffalo for ex-situ conservation. Using the comparative intradermal tuberculin test (CIDT) the BTB status at both individual animal and herd level was estimated to be 0.0% by the CIDT technique. Compared to Avian reactors only, a prevalence of 5.8% was determined whilst for Bovine-only reactors a prevalence of 0.0% was determined. These results suggest the likelihood of buffalo herds in the Kafue National Park being free of BTB

Thelazia rhodesii in the African Buffalo, Syncerus caffer, in Zambia

We report 2 cases of Thelazia rhodesii infection in the African buffaloes, Syncerus caffer, in Zambia. African buffalo calves were captured from the livestock and wildlife interface area of the Kafue basin in the dry season of August 2005 for the purpose to translocate to game ranches. At capture, calves (n=48) were examined for the presence of eye infections by gently manipulating the orbital membranes to check for eye-worms in the conjunctival sacs and corneal surfaces. Two (4.3%) were infected and the mean infection burden per infected eye was 5.3 worms (n=3). The mean length of the worms was 16.4 mm (95% CI; 14.7-18.2 mm) and the diameter 0.41 mm (95% CI; 0.38-0.45 mm). The surface cuticle was made of transverse striations which gave the worms a characteristic serrated appearance. Although the calves showed signs of kerato-conjunctivitis, the major pathological change observed was corneal opacity. The calves were kept in quarantine and were examined thrice at 30 days interval. At each interval, they were treated with 200 µg/kg ivermectin, and then translocated to game ranches. Given that the disease has been reported in cattle and Kafue lechwe (Kobus lechwe kafuensis) in the area, there is a need for a comprehensive study which aims at determining the disease dynamics and transmission patterns of thelaziasis between wildlife and livestock in the Kafue basin

Detection of Babesia spp. in Free-Ranging Pukus, Kobus vardonii, on a Game Ranch in Zambia

Babesia spp. were detected from 4 asymptomatic pukus captured on a game ranch in central Zambia in October 2008. Blood smears were examined in 4 species of aymptomatic free-ranging antelopes, namely the puku (Kobus vordanii), reedbuck (Redunca arundinum), bushbuck (Tragelaphus sylvaticus), and kudu (Tragelaphus strepsiceros), and showed the presence of Babesia parasites only in the puku. In the puku, the prevalence of babesiosis was estimated at 33.3% (n=12), while the overall prevalence in all examined animals was 8.5% (n=47). The parasites showed morphological characteristics of paired ring-like stages with the length varying between 1.61 µm and 3.02 µm (mean=2.12 µm, n=27; SD=0.76 µm). Both the infected and non-infected pukus showed good body condition scores (BCS), while the dominant tick species detected from all animals were Rhipicephalus appendiculatus, Rhipicephalus spp., and Boophilus spp. To our knowledge this is the first report of Babesia spp. infection in pukus in Zambia. These findings suggest that wildlife could play an important role in the epidemiology of babesiosis in Zambia

An overview of challenges limiting the design of protective mucosal vaccines for finfish

Research in mucosal vaccination in finfish has gained prominence in the last decade in pursuit of mucosal vaccines that would lengthen the duration of protective immunity in vaccinated fish. However, injectable vaccines have continued to dominate in the vaccination of finfish because they are perceived to be more protective than mucosal vaccines. Therefore, it has become important to identify the factors that limit developing protective mucosal vaccines in finfish as an overture to identifying key areas that require optimization in mucosal vaccine design. Some of the factors that limit the success for designing protective mucosal vaccines for finfish identified in this review include the lack optimized protective antigen doses for mucosal vaccines, absence of immunostimulants able to enhance the performance of non-replicative mucosal vaccines, reduction of systemic antibodies due to prolonged exposure to oral vaccination and the lack of predefined correlates of protective immunity for use in the optimization of newly developed mucosal vaccines. This review also points out the need to develop prime-boost vaccination regimes able to induce long-term protective immunity in vaccinated fish. By overcoming some of the obstacles identified herein it is anticipated that future mucosal vaccines shall be designed to induce long-term protective immunity in finfish

A review of the immunological mechanisms following mucosal vaccination of finfish

Mucosal organs are principle portals of entry for microbial invasion and as such developing protective vaccines against these pathogens can serve as a first line of defense against infections. In general, all mucosal organs in finfish are covered by a layer of mucus whose main function is not only to prevent pathogen attachment by being continuously secreted and sloughing-off but it serves as a vehicle for antimicrobial compounds, complement and immunoglobulins that degrade, opsonize and neutralize invading pathogens on mucosal surfaces. In addition, all mucosal organs in finfish possess antigen presentation cells (APCs) that activate cells of the adaptive immune system to generate long lasting protective immune responses. The functional activities of APCs are orchestrated by a vast array of proinflammatory cytokines and chemokines found in all mucosal organs. The adaptive immune system in mucosal organs is made of humoral immune responses able to neutralize invading pathogens as well as cellular mediated immune responses whose kinetics are comparable to those induced by parenteral vaccines. In general, finfish mucosal immune system has the capacity to serve as the first line defense mechanism against microbial invasion as well as being responsive to vaccination