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The changing landscape of rabies epidemiology and control
2014
Sarah Cleaveland | Hawthorne Beyer | Katie Hampson | Daniel Haydon | Felix Lankester | Tiziana Lembo | Francois-Xavier Meslin | Michelle Morters | Zacharia Mtema | Maganga Sambo | Sunny Townsend
Over the past 20 years, major progress has been made in our understanding of critical aspects of rabies epidemiology and control. This paper presents results of recent research, highlighting methodological advances that have been applied to burden of disease studies, rabies epidemiological modelling and rabies surveillance. These results contribute new insights and understanding with regard to the epidemiology of rabies and help to counteract misperceptions that currently hamper rabies control efforts in Africa. The conclusion of these analyses is that the elimination of canine rabies in Africa is feasible, even in wildlife-rich areas, through mass vaccination of domestic dogs and without the need for indiscriminate culling to reduce dog population density. Furthermore, the research provides valuable practical insights that support the operational planning and design of dog vaccination campaigns and rabies surveillance measures.
显示更多 [+] 显示较少 [-]The changing landscape of public health in sub-Saharan Africa: Control and prevention of communicable diseases needs rethinking
2014
Leonard E.G. Mboera | Sayoki G. Mfinanga | Esron D. Karimuribo | Susan F. Rumisha | Calvin Sindato
In sub-Saharan Africa, communicable diseases (CDs) are the leading public health problems and major causes of morbidity and mortality. CDs result in significant individual suffering, disrupting daily life, threatening livelihoods and causing one-third of the years lost to illness or death worldwide. This paper aims to analyse the current strategies in the control and prevention of CDs in sub-Saharan Africa and proposes an ecohealth approach in relation to current changing epidemiological profiles. Whilst in recent years the burden of HIV and AIDS, tuberculosis and malaria have helped to mobilise large amounts of funding and expertise to help address them, many CDs, particularly those affecting the poor, have been neglected. People living in rural areas are also likely to be politically marginalised and living in degraded environments. They often lack assets, knowledge and opportunities to gain access to health care or protect themselves from infections. New diseases are also emerging at unprecedented rates and require attention. Many CDs are rooted in environmental and livelihood conditions and mediated by social and individual determinants. It is now increasingly recognised that a much broader, coordinated and multi-sectoral ecohealth approach is required to address CDs in sub-Saharan Africa. An ecohealth approach has been shown to be more robust in public health interventions than the traditional medical approach. The approach helps to generate an understanding of ecosystem factors that influence the emergence and spread of both old and new diseases, considers temporal and spatial dimensions of disease infection and allows systems thinking. In conclusion, establishing intersectoral and multisectoral linkages is important to facilitate joint efforts to address CDs at the national, district and community levels.
显示更多 [+] 显示较少 [-]Spatial and temporal distribution of foot-and-mouth disease virus in the lake zone of Tanzania
2014
Joseph M. Genchwere | Christopher J. Kasanga
This study was conducted to determine the spatiotemporal distribution of foot-and-mouth disease (FMD) virus (FMDV) serotypes and evaluate the awareness of livestock keepers about FMD in Tanzania. An observational prospective study involving serological analysis, FMDV antigen detection and questionnaire survey was carried out in the lake zone of Tanzania. Seroprevalence of antibodies to the nonstructural protein 3ABC of FMDV and serotype-specific antigen detection were investigated by using SVANOVIR® FMDV 3ABC-Ab ELISA and indirect-sandwich ELISA (sELISA), respectively, whilst a structured questionnaire was used to evaluate the awareness of livestock keepers about FMD. During the period of 2010–2011, both serum and tissue (foot-and-mouth epithelia) samples were collected from cattle suspected of FMD in 13 districts of the four regions of the lake zone. A total of 107 (80.5%) out of 133 tested serum samples were seropositive to nonstructural protein 3ABC, with at least one sample being positive from all 10 districts screened. Fifteen (53.6%) out of 28 tissue epithelial samples collected from FMD cases in eight districts during the course of this study were positive to serotype O FMDV antigen. Of these eight districts, serotype O FMDV antigens were detected from seven districts and no other serotypes were recovered from animal samples screened. Questionnaire surveys in six districts indicated that livestock keepers in the lake zone were aware of the clinical manifestations (26/29 = 90.0%) and economic impact (23/29 = 79.0%) of FMD in the region. The questionnaire data showed that FMD outbreaks often occurred after rainy seasons (22/29 = 75.9%), with the highest peaks predominantly occurring just after the long rains in May and June, and at the end of the short rains in November and December of each year. The spatial distribution of the FMD cases suggested that serotype O virus exposure was the only widespread cause of the 2010–2011 outbreaks in the lake zone.
显示更多 [+] 显示较少 [-]Evaluation of medicinal turpentine used for the prevention of bovine babesiosis in southern KwaZulu-Natal and the eastern Free State
2014
Louise J. Biggs | Chris A.P. Carrington | Vinny Naidoo
Medicinal turpentine has been used extensively in the eastern Free State and KwaZulu-Natal provinces of South Africa with reportedly excellent results. It is believed that it is able to prevent and treat babesiosis (redwater) in cattle. Redwater is an often-fatal disease in cattle and results in losses of large numbers every year in South Africa. This study was initiated in an attempt to investigate the validity of the use of the turpentine as a medicinal agent. Using a semi in vitro screening assay, Babesia caballi grown in primary equine erythrocytes was exposed to various concentrations of turpentine in comparison to diminazene and imidocarb. The turpentine had no parasiticidal effect following direct exposure. During the recovery phase, the previously exposed parasites appeared to grow more slowly than the controls. In comparison, diminazene and imidocarb were 100% effective in killing the parasites. In a subsequent tolerance study in adult cattle (n = 6) at 1x (2 mL), 3x and 5x the recommended dose, the product was non-toxic. Irritation was noted at the injection site with the higher dose. The only major finding on clinical pathology was a general increase in globulins, without a concurrent change in native babesia antibody titres. It was concluded that it is unlikely that medicinal turpentine is an effective treatment against babesiosis.
显示更多 [+] 显示较少 [-]Virulence of <i>Trypanosoma congolense</i> strains isolated from cattle and African buffaloes (<i>Syncerus caffer</i>) in KwaZulu-Natal, South Africa
2014
Makhosazana Y. Motloang | Justin Masumu | Ben J. Mans | Abdalla A. Latif
Trypanosoma congolense and Trypanosoma vivax are major species that infect cattle in north-eastern KwaZulu-Natal (KZN), South Africa. Of the two genetically distinct types of T. congolense, Savannah and Kilifi sub-groups, isolated from cattle and tsetse flies in KZN, the former is more prevalent and thought to be responsible for African animal trypanosomosis outbreaks in cattle. Furthermore, variation in pathogenicity within the Savannah sub-group is ascribed to strain differences and seems to be related to geographical locations. The objective of the present study was to compare the virulence of T. congolense strains isolated from African buffaloes (Syncerus caffer) inside Hluhluwe-iMfolozi Park, and from cattle on farms near wildlife parks (< 5 km), to isolates from cattle kept away (> 10 km) from parks. To obtain T. congolense isolates, blood of known parasitologically positive cattle or cattle symptomatically suspect with trypanosomosis, as well as isolates from buffaloes kept inside Hluhluwe-iMfolozi Park were passaged in inbred BALB/c mice. A total of 26 T. congolense isolates were obtained: 5 from buffaloes, 13 from cattle kept near parks and 8 from cattle distant from parks. Molecular characterisation revealed 80% and 20% of isolates to belong to T. congolense Savannah and Kilifi, respectively. To compare virulence, each isolate was inoculated into a group of six mice. No statistical differences were observed in the mean pre-patent period, maximum parasitaemia or drop in packed cell volume (PCV). Significant differences were found in days after infection for the drop in PCV, the patent period and the survival time. These differences were used to categorise the isolates as being of high, moderate or low virulence. Based on the virulence, 12 of 26 (46%) isolates were classified as highly virulent and 27% each as either of moderate or of low virulence. Whilst 11 of 12 high virulent strains were from buffaloes or cattle near the park, only 1 of 7 low virulent strains was from these animals. All the Kilifi T. congolense types were less virulent than the Savannah types. These results confirmed the higher virulence of T. congolense Savannah type compared to Kilifi type and indicated the prevalence of highly virulent strains to be higher in wildlife parks and in cattle near the parks than on farms further away. The geographical location of these strains in relation to the wildlife parks in the area was discussed.
显示更多 [+] 显示较少 [-]Foot and mouth disease in Zambia: Spatial and temporal distributions of outbreaks, assessment of clusters and implications for control
2014
Yona Sinkala | Martin Simuunza | John B. Muma | Dirk U. Pfeiffer | Christopher J. Kasanga | Aaron Mweene
Zambia has been experiencing low livestock productivity as well as trade restrictions owing to the occurrence of foot and mouth disease (FMD), but little is known about the epidemiology of the disease in these endemic settings. The fundamental questions relate to the spatio-temporal distribution of FMD cases and what determines their occurrence. A retrospective review of FMD cases in Zambia from 1981 to 2012 was conducted using geographical information systems and the SaTScan software package. Information was collected from peer-reviewed journal articles, conference proceedings, laboratory reports, unpublished scientific reports and grey literature. A space–time permutation probability model using a varying time window of one year was used to scan for areas with high infection rates. The spatial scan statistic detected a significant purely spatial cluster around the Mbala–Isoka area between 2009 and 2012, with secondary clusters in Sesheke–Kazungula in 2007 and 2008, the Kafue flats in 2004 and 2005 and Livingstone in 2012. This study provides evidence of the existence of statistically significant FMD clusters and an increase in occurrence in Zambia between 2004 and 2012. The identified clusters agree with areas known to be at high risk of FMD. The FMD virus transmission dynamics and the heterogeneous variability in risk within these locations may need further investigation.
显示更多 [+] 显示较少 [-]Distribution patterns and predilection muscles of <i>Trichinella zimbabwensis</i> larvae in experimentally infected Nile crocodiles (<i>Crocodylus niloticus</i> Laurenti)
2014
Louis J. La Grange | Samson Mukaratirwa
No controlled studies have been conducted to determine the predilection muscles of Trichinella zimbabwensis larvae in Nile crocodiles (Crocodylus niloticus) or the influence of infection intensity on the distribution of the larvae in crocodiles. The distribution of larvae in muscles of naturally infected Nile crocodiles and experimentally infected caimans (Caiman crocodilus) and varans (Varanus exanthematicus) have been reported in literature. To determine the distribution patterns of T. zimbabwensis larvae and predilection muscles, 15 crocodiles were randomly divided into three cohorts of five animals each, representing high infection (642 larvae/kg of bodyweight average), medium infection (414 larvae/kg of bodyweight average) and low infection (134 larvae/kg of bodyweight average) cohorts. In the high infection cohort, high percentages of larvae were observed in the triceps muscles (26%) and hind limb muscles (13%). In the medium infection cohort, high percentages of larvae were found in the triceps muscles (50%), sternomastoid (18%) and hind limb muscles (13%). In the low infection cohort, larvae were mainly found in the intercostal muscles (36%), longissimus complex (27%), forelimb muscles (20%) and hind limb muscles (10%). Predilection muscles in the high and medium infection cohorts were similar to those reported in naturally infected crocodiles despite changes in infection intensity. The high infection cohort had significantly higher numbers of larvae in the sternomastoid, triceps, intercostal, longissimus complex, external tibial flexor, longissimus caudalis and caudal femoral muscles (p < 0.05) compared with the medium infection cohort. In comparison with the low infection cohort, the high infection cohort harboured significantly higher numbers of larvae in all muscles (p < 0.05) except for the tongue. The high infection cohort harboured significantly higher numbers of larvae (p < 0.05) in the sternomastoid, triceps, intercostal, longissimus complex, external tibial flexor, longissimus caudalis and caudal femoral muscles compared with naturally infected crocodiles. Results from this study show that, in Nile crocodiles, larvae of T. zimbabwensis appear first to invade predilection muscles closest to their release site in the small intestine before occupying those muscles situated further away. The recommendation for the use of masseter, pterygoid and intercostal muscles as sampling sites for the detection of T. zimbabwensis in crocodiles is in contrast to the results from this study, where the fore- and hind limb muscles had the highest number of larvae. This study also supports the use of biopsy sampling from the dorso-lateral regions of the tail for surveillance purposes in both wild and commercial crocodile populations.
显示更多 [+] 显示较少 [-]Drivers of disease emergence and spread: Is wildlife to blame?
2014
Richard Kock
The global focus on wildlife as a major contributor to emerging pathogens and infectious diseases (EIDs) in humans and domestic animals is not based on field, experimental or dedicated research, but mostly on limited surveys of literature, opinion and the assumption that biodiversity harbours pathogens. The perceived and direct impacts of wildlife, from being a reservoir of certain human and livestock pathogens and as a risk to health, are frequently overstated when compared to the Global burden of disease statistics available from WHO, OIE and FAO. However organisms that evolve in wildlife species can and do spill-over into human landscapes and humans and domestic animal population and, where these organisms adapt to surviving and spreading amongst livestock and humans, these emerging infections can have significant consequences. Drivers for the spill-over of pathogens or evolution of organisms from wildlife reservoirs to become pathogens of humans and domestic animals are varied but almost without exception poorly researched. The changing demographics, spatial distribution and movements, associated landscape modifications (especially agricultural) and behavioural changes involving human and domestic animal populations are probably the core drivers of the apparent increasing trend in emergence of new pathogens and infectious diseases over recent decades.
显示更多 [+] 显示较少 [-]The benefits of ‘One Health’ for pastoralists in Africa
2014
Helena Greter | Vreni Jean-Richard | Lisa Crump | Mahamat Béchir | Idriss O. Alfaroukh | Esther Schelling | Bassirou Bonfoh | Jakob Zinsstag
‘One health’ is particularly suited to serve mobile pastoralists. Dinka pastoralists in Sudan inspired Calvin Schwabe to coin the term ‘one medicine’, indicating that there is no difference in paradigm between human and veterinary medicine. Our contemporary definition of ‘one health’ is any added value in terms of improved health of humans and animals or financial savings or environmental services resulting from a closer cooperation of human and animal health sectors. Here we present a summary of ‘one health’ studies with mobile pastoralists in Africa which were done in research partnership, demonstrating such an added value. Initial joint human and animal health studies revealed higher livestock vaccination coverage than in the pastoralist community, leading to joint animal and human vaccination intervention studies which demonstrated a better access to primary health care services for pastoralists in Chad. Further simultaneous animal and human serological studies showed that camel breeding was associated with human Q-fever seropositivity. In Borana communities in Ethiopia, human cases of Mycobacterium bovis infection could be related to strains isolated from cattle. A challenge remained with regard to how to assess vaccination coverage in mobile populations. With the advent of mobile phones, health and demographic surveillance could be established for mobile pastoralists and their animals. This presents vast possibilities for surveillance and control of human and animal diseases. Pastoralists prefer a ‘one health’ approach and therefore contribute toward the validation of this concept by showing real added value of the cooperation between human and animal health services.
显示更多 [+] 显示较少 [-]Two genotypes of infectious bronchitis virus are responsible for serological variation in KwaZulu-Natal poultry flocks prior to 2012
2014
Adrian D. Knoetze | Niloshni Moodley | Celia Abolnik
This study describes the isolation, serotyping and genotyping of 54 infectious bronchitis virus (IBV) cases predominantly in KwaZulu-Natal and compared to several isolates from other South African provinces between 2011 and 2012 and several historic isolates. The results indicate the division of isolates into two different genotypes of IBV within the province, Massachusetts (Mass)-like and QX-like. The IBV Mass-like genotype was the most prevalent and was detected in 79% of the full spike protein S1 gene sequences. Variation up to 22.3% was detected within local Mass-type strains, supporting the hypothesis that multiple IBV serotypes may co-circulate in the same region simultaneously. Additionally, more conservation was observed amongst Mass serotypes versus QX-like serotypes, implying that vaccine use can influence the variability within the IBV population; this is deduced from the fact that the only live vaccine registered for use in South Africa at the time of the study was of Mass origin and no QX-like vaccines were available for use. This study offers the first published consolidation of IBV isolates from an area of South Africa and identifies variation within the IBV population of the broiler flock within the study area over a 2-year period.
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