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Echinococcosis in sub-Saharan Africa: Emerging complexity

Parasitology Unit, University of Hohenheim, 70599 Stuttgart, Germany.
Veterinary Parasitology (Impact Factor: 2.46). 04/2011; 181(1):43-7. DOI: 10.1016/j.vetpar.2011.04.022
Source: PubMed

ABSTRACT

Cystic echinococcosis occurs in most regions of sub-Saharan Africa, but the frequency of this zoonosis differs considerably among and within countries. Especially human cases seem to be focally distributed. A number of environmental and behavioural factors partially explain this pattern, i.e. density of livestock, presence of dogs, uncontrolled slaughter, and hygiene. In addition, the various taxa of Echinococcus spp. are known to differ considerably in infectivity to different host species including humans. Genetic characterizations of isolates, which are necessary to evaluate the impact of this factor - so far done in only a few countries - indicate that the diversity of Echinococcus spp. in Sub-Saharan Africa is greater than on any other continent. The very incomplete data which are available show that sympatrical taxa may infect different hosts, others may be geographically restricted, some life cycles involve livestock, others wild animals. Possible implications of this complexity for public health, livestock economy and conservation are briefly discussed.

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    • "Hailemariam et al. (2012) found 35 G1 (from sheep, cattle and camels) and five G6 (from camels and cattle) in cysts collected in abattoirs in Addis Ababa and East Ethiopia. Romig et al. (2011) reported an unpublished study by Romig and Dinkel who identified E. granulosus G1, E. ortleppi G5 and G6/G7 among 21 cysts from cattle in North Ethiopia. Human CE was reported from different parts of the country (Minas et al., 2007; Kebede et al., 2009; Macpherson et al., 1989a; Fuller and Fuller, 1981) but the overall public health impact is not known. "
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    ABSTRACT: Cystic Echinococcosis (CE) caused by Echinococcus granulosus sensu lato (s.l.) is a neglected helminth zoonosis affecting humans and various animal species. Human CE has been reported in almost all countries of sub-Saharan Africa but its prevalence and public health impact are subject to large geographical variations. The reasons for these differences are not well understood; among other factors, occurrence of different species/genotypes of E. granulosus s.l. has been suggested. CE is very common in all livestock species in Ethiopia; human CE is poorly documented in the country. The aim of this study was to assess the fertility and molecularly characterize hydatid cysts collected from cattle, camels, goats and pigs from different parts of the country. From the 137 samples characterized by PCR-RFLP and sequencing, 115 (83.9%) were identified as E. granulosus s.s. (G1, common sheep strain), 6 (4.4%) as E. ortleppi (G5, cattle strain) and 16 (11.7%) as E. intermedius (G6/7, camel strain). In cattle, E. granulosus s.s. and E. ortleppi were found; in camels and goats, E. granulosus s.s. and E. intermedius; two cysts found in pigs were identified as E. granulosus s.s. and E. ortleppi, respectively. All cysts recovered from goats and pigs were sterile, while fertility was 34% and 50% in cysts from cattle and camels, respectively. In cattle, 31% of E. granulosus s.s. cysts were fertile, showing the importance of cattle in the transmission of the “sheep strain”. Next to E. granulosus s.s., E. intermedius (camel strain) was the predominant species: 34.4% of the cysts collected from camels and 62.5% from goats were identified as E. intermedius. These animals originated from the drier Central, Eastern and Southern parts of the country. For the first time, we showed the presence of CE in pigs in Ethiopia. The presence of these strains and especially the fact that the zoonotic E. granulosus s.s. and E. intermedius are dominant, make CE an important public health concern in Ethiopia
    Full-text · Article · Oct 2015 · Veterinary Parasitology
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    • "Cystic echinococcosis (CE) caused by larval stages of Echinococcus granulosus is one of the most common zoonotic diseases associated with severe economic losses and great public health significance worldwide (Romig et al. 2011). Echinococcus infections are estimated to affect approximately two to three million people worldwide, with Africa amongst the primarily endemic regions (Cummings, Rodriguez-Sosa & Satoskar 2009). "
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    ABSTRACT: This study was conducted to determine the prevalence of cystic echinococcosis (CE) in small ruminants and humans in Addis Ababa, central Ethiopia. A cross-sectional study involving systematic random sampling was conducted to estimate the prevalence of CE in 512 small ruminants (262 sheep and 250 goats) slaughtered at Addis Ababa Abattoir Enterprise between October 2011 and March 2012. Hydatid cysts were identified macroscopically during postmortem examination and their fertility and viability were determined. CE was observed in 21 (8.02%) sheep and 17 (6.80%) goats. In sheep 13 (4.96%) of the lungs, 10 (3.81%) livers and 1 (0.381%) heart were found to be infected with hydatid cysts. Involvement of lung and liver in goats was found to be 10 (4.0%) and 8 (3.2%) respectively, with no cysts recorded in the heart. Of the total of 77 and 47 cysts encountered in sheep and goats, 33 (42.85%) and 15 (31.91%) respectively were fertile. Viability of protoscoleces from fertile cysts in sheep (29 [87.87%]) was higher than in goats (6 [40.0%]). For humans, retrospective analysis covering five years of case reports at two major hospitals in Addis Ababa between January 2008 and December 2012 showed that of the total of 25 840 patients admitted for ultrasound examination, 27 CE cases were registered, a prevalence of 0.1% and mean annual incidence rate of approximately 0.18 cases per 100 000 population. Liver was the major organ affected in humans (81.5% in affected patients) followed by spleen (11.1%) and kidney (7.4%). Logistic regression analysis showed that prevalence of CE varied significantly in relation to host age in the small ruminants (OR = 3.93, P < 0.05) as well as in humans (95% CI, R = 4.8). This epidemiological study confirms the importance of CE in small ruminants and humans in central Ethiopia, emphasising the need for integrated approaches to controlling this neglected preventable disease.
    Full-text · Article · Aug 2015
    • "Eastern Europe, Sudan/Egypt, northern parts of Eurasia and North America ) and some case reports indicated a benign course of disease (Wilson et al., 1968). Also, in areas of East Africa, where both E. canadensis (G6) and E. granulosus s.s. are frequent in animals, only a small proportion of patients were found infected with the former species (Romig et al., 2011); a similar situation seems to prevail in North Africa and the Middle East (Alvarez Rojas et al., 2014). Yet, the contribution to global disease load is not negligible, as in a worldwide conspectus of 1661 human cases, 184 (11.07%) were caused by G6 or G7 (only two cases by G8 or G10). "
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    ABSTRACT: Echinococcus granulosus, formerly regarded as a single species with a high genotypic and phenotypic diversity, is now recognised as an assemblage of cryptic species, which differ considerably in morphology, development, host specificity (including infectivity/pathogenicity for humans) and other aspects. This diversity is reflected in the mitochondrial and nuclear genomes and has led to the construction of phylogenetic trees and hypotheses on the origin and geographic dispersal of various taxa. Based on phenotypic characters and gene sequences, E. granulosus (sensu lato) has by now been subdivided into E. granulosus sensu stricto (including the formerly identified genotypic variants G1-3), Echinococcus felidis (the former 'lion strain'), Echinococcus equinus (the 'horse strain', genotype G4), Echinococcus ortleppi (the 'cattle strain', genotype G5) and Echinococcus canadensis. The latter species, as recognised here, shows the highest diversity and is composed of the 'camel strain', genotype G6, the 'pig strain', genotype G7, and two 'cervid strains', genotypes G8 and G10. There is debate whether the closely related G6 and G7 should be placed in a separate species, but more morphological and biological data are needed to support or reject this view. In this classification, the application of rules for zoological nomenclature led to the resurrection of old species names, which had before been synonymised with E. granulosus. This nomenclatural subdivision of the agents of cystic echinococcosis (CE) may appear inconvenient for practical applications, especially because molecular tools are needed for identification of the cyst stage, and because retrospective data on 'E. granulosus' are now difficult to interpret without examination of voucher specimens. However, the increased awareness for the diversity of CE agents - now emphasised by species names rather than genotype numbers - has led to a large number of recent studies on this issue and a rapid increase of knowledge on geographical spread, host range and impact on human health of the various species. E. granulosus s.s., often transmitted by sheep, is now clearly identified as the principal CE agent affecting humans. Contrary to previous assumptions, genotypes G6/7 of E. canadensis readily infect humans, although CE incidences are rather low where E. canadensis predominates. Sub-Saharan Africa seems to be the region with the highest diversity of Echinococcus, and wild carnivores may play a more important role in the lifecycles of various species than previously assumed. Still, a number of issues remain unclear, e.g. possibly diverging parameters of diagnostic tests among the species, different responses to vaccines and, importantly, possibly required modifications of clinical management due to differences in pathogenicity. Copyright © 2015 Elsevier B.V. All rights reserved.
    No preview · Article · Jul 2015 · Veterinary Parasitology
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