Serologic survey of human hydatid disease in high risk populations from central Tunisia. Preliminary results

Africa-wide meta-analysis on the prevalence and distribution of human cystic echinococcosis and canine Echinococcus granulosus infections

BACKGROUND

Echinococcosis is a neglected zoonosis of increasing public health concern worldwide. According to the World Health Organization, 19,300 lives and 871,000 disability-adjusted life-years are lost globally each year because of cystic echinococcosis. Annual costs associated with cystic echinococcosis were estimated at US$ 3 billion because of treatment of cases and losses in the livestock industry.

METHODS

We performed the random-effects model of meta-analysis using 51-year (1970-2021) data available from AJOL, Google Scholar, PubMed, Science Direct, Scopus and Web of Science. We also applied the Joanna Briggs Institute critical appraisal instrument for studies reporting prevalence data, the Cochran's Q-test, Egger's regression test and the single study deletion technique to respectively examine within-study bias, heterogeneity, across-study bias and sensitivity.

RESULTS

Thirty-nine eligible studies on human cystic echinococcosis (HCE) from 13 countries across the five African sub-regions showed an overall prevalence of 1.7% (95% CI 1.1, 2.6) with a statistically significant (P < 0.001) sub-group range of 0.0% (95% CI 0.0, 14.1) to 11.0% (95% CI 7.6, 15.7). Highest prevalences were observed in Eastern Africa (2.7%; 95% CI 1.4, 5.4) by sub-region and Sudan (49.6%; 95% 41.2, 58.1) by country. Another set of 42 studies on Echinococcus granulosus infections (EGI) in dogs from 14 countries across the five African sub-regions revealed an overall prevalence of 16.9% (95% CI 12.7, 22.3) with a significant (P < 0.001) variation of 0.4 (95% CI 0.0, 5.9) to 35.8% (95% CI 25.4, 47.8) across sub-groups. Highest prevalences of E. granulosus were observed in North Africa (25.6%; 95% CI 20.4, 31.6) by sub-region and Libya (9.2%; 95% CI 5.7, 13.9) by country.

CONCLUSION

Human cystic echinococcosis and EGI are respectively prevalent among Africans and African dogs. We recommend a holistic control approach that targets humans, livestock, dogs and the environment, which all play roles in disease transmission. This approach should involve strategic use of anthelminthics in animals, standardized veterinary meat inspection in abattoirs, control of stray dogs to reduce environmental contamination and proper environmental sanitation. Mass screening of humans in hyper-endemic regions will also encourage early detection and treatment.

Epidemiology and strain characteristics of Echinococcus granulosus in the Benghazi area of eastern Libya

The incidence of surgically confirmed cystic echinococcosis in eastern Libya was estimated to be at least 4.2 cases/100,000, with significantly more female cases than male. The prevalences of infection with Echinococcus granulosus among 1087 sheep, 881 goats, 428 camels and 614 cattle from the same region, determined postmortem in abattoirs, were 20%, 3.4%, 13.6% and 11%, respectively. Infection in the livestock was age-dependent and, generally, the female animals were more often infected than the male. The measurements of rostellar hooks on protoscoleces collected from sheep and cattle were similar but significantly different from the corresponding measurements of parasites of human or camel origin. However, when a portion of the cytochrome c-oxidase subunit I (cox1) gene from each of 30 protoscolex samples from Libya (12 from cattle, three from humans, five from camels and 10 from sheep) was sequenced, the sequences were all found to be identical to that published for the common sheep strain of E. granulosus.

Public health aspects of cystic echinococcosis in the Arab countries

Human cystic echinococcosis (CE) caused by larval Echinococcus granulosus is a zoonosis of major public health importance throughout the region comprising Arab North Africa and the Middle East. Prevalence rates are determined by epizootiological factors related to the size of stray dog population and its worm burden and to the infection rates in the intermediate host reservoir livestock population. Socio-economic development and socio-cultural practices are considered important determinants in the continued transmission of the disease. The reasons why CE remains a significant public health problem in the region are summarized.

Echotomographic and serological population-based study of hydatidosis in central Tunisia

A population-based echotomographic (ECT) and serological survey of hydatidosis was carried out in a high risk community located in Central Tunisia. 1434 subjects over 5 years of age (93.3% of the population in this age range) underwent an abdominal echotomography (ECT) and a serological test (ELISA with confirmation by counterelectrophoresis). The ECT prevalence rate was 3.5% and increased with age reaching 7.7% in the over 39 years age group. Most subjects (96.0%) had liver cyst(s). The serological prevalence rate was 2.9%. A strong agreement was found between ECT and serological results (Kappa test = 0.449). Taking ECT as a reference, the relative specificity and sensitivity of serology were 99.3 and 62.0 respectively. Most ECT positive seronegative subjects had calcified cysts. These results confirm the presence of highly endemic foci of hydatidosis in Central Tunisia, show a good agreement between serological and ECT results at a population level and demonstrate the high feasibility of ECT as a screening technique.

Distribution of surgical hydatidosis in central Tunisia (1982-1985)

The mean annual surgical incidence rates (MASIR) of hydatidosis were measured for the 1982-1985 period in central Tunisia in order to investigate the natural history of human hydatidosis and provide baseline data for the evaluation of future prevention campaigns. 986 cases were identified from surgical records of regional hospitals to which cases from central Tunisia are mandatorily referred. The overall MASIR was 19.3 per 10(5) inhabitants. The MASIR according to district varied from 0 to 56.6 per 10(5), was higher in women than in men (22.6 versus 15.8 per 10(5] and increased with age (maximum 53.0 per 10(5) in the 50-59 age group for women and 27.1 per 10(5) in the 40-49 group for men). Among the 940 cases with single organ hydatidosis, liver ranged first (55.3%, 545/940), then lung (32.4% 320/940), kidney (2.7%) and spleen (1.8%). Among the 865 subjects with single lung or liver hydatidosis, liver was more often involved in women (349 out of 503) than in men (196 out of 362) (chi 2 = 20.9, p less than 0.001). In both sexes, the lung/liver ratio decreased with age. These data reveal the existence of highly endemic foci of hydatidosis within central Tunisia. The predominance of infection in women might be due to sex related behavioral differences. The causes of liver predominance in women and variation of lung/liver ratio are open to question.