Petra Kern

European Echinococcosis Registry: Human Alveolar Echinococcosis, Europe, 1982–2000

Surveillance for alveolar echinococcosis in central Europe was initiated in 1998. On a voluntary basis, 559 patients were reported to the registry. Most cases originated from rural communities in regions from eastern France to western Austria; single cases were reported far away from the disease-“endemic” zone throughout central Europe. Of 210 patients, 61.4% were involved in vocational or part-time farming, gardening, forestry, or hunting. Patients were diagnosed at a mean age of 52.5 years; 78% had symptoms. Alveolar echinococcosis primarily manifested as a liver disease. Of the 559 patients, 190 (34%) were already affected by spread of the parasitic larval tissue. Of 408 (73%) patients alive in 2000, 4.9% were cured. The increasing prevalence of Echinococcus multilocularis in foxes in rural and urban areas of central Europe and the occurrence of cases outside the alveolar echinococcosis–endemic regions suggest that this disease deserves increased attention.

Risk Factors for Alveolar Echinococcosis in Humans

A case-control study of alveolar echinococcosis cases in Germany identifies several risk factors for the disease.

Echinococcosis in sub-Saharan Africa: emerging complexity.

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.

Sensitive and Specific Immunohistochemical Diagnosis of Human Alveolar Echinococcosis with the Monoclonal Antibody Em2G11

Background Alveolar echinococcosis (AE) is caused by the metacestode stage of Echinococcus multilocularis. Differential diagnosis with cystic echinococcosis (CE) caused by E. granulosus and AE is challenging. We aimed at improving diagnosis of AE on paraffin sections of infected human tissue by immunohistochemical testing of a specific antibody. Methodology/Principal Findings We have analysed 96 paraffin archived specimens, including 6 cutting needle biopsies and 3 fine needle aspirates, from patients with suspected AE or CE with the monoclonal antibody (mAb) Em2G11 specific for the Em2 antigen of E. multilocularis metacestodes. In human tissue, staining with mAb Em2G11 is highly specific for E. multilocularis metacestodes while no staining is detected in CE lesions. In addition, the antibody detects small particles of E. multilocularis (spems) of less than 1 µm outside the main lesion in necrotic tissue, liver sinusoids and lymphatic tissue most probably caused by shedding of parasitic material. The conventional histological diagnosis based on haematoxylin and eosin and PAS stainings were in accordance with the immunohistological diagnosis using mAb Em2G11 in 90 of 96 samples. In 6 samples conventional subtype diagnosis of echinococcosis had to be adjusted when revised by immunohistology with mAb Em2G11. Conclusions/Significance Immunohistochemistry with the mAb Em2G11 is a new, highly specific and sensitive diagnostic tool for AE. The staining of small particles of E. multilocularis (spems) outside the main lesion including immunocompetent tissue, such as lymph nodes, suggests a systemic effect on the host.

A survey for Echinococcus spp. of carnivores in six wildlife conservation areas in Kenya.

To investigate the presence of Echinococcus spp. in wild mammals of Kenya, 832 faecal samples from wild carnivores (lions, leopards, spotted hyenas, wild dogs and silver-backed jackals) were collected in six different conservation areas of Kenya (Meru, Nairobi, Tsavo West and Tsavo East National Parks, Samburu and Maasai Mara National Reserves). Taeniid eggs were found in 120 samples (14.4%). In total, 1160 eggs were isolated and further analysed using RFLP-PCR of the nad1 gene and sequencing. 38 of these samples contained eggs of Echinococcus spp., which were identified as either Echinococcus felidis (n=27) or Echinococcus granulosus sensu stricto (n=12); one sample contained eggs from both taxa. E. felidis was found in faeces from lions (n=20) and hyenas (n=5) while E. granulosus in faeces from lions (n=8), leopards (n=1) and hyenas (n=3). The host species for two samples containing E. felidis could not be identified with certainty. As the majority of isolated eggs could not be analysed with the methods used (no amplification), we do not attempt to give estimates of faecal prevalences. Both taxa of Echinococcus were found in all conservation areas except Meru (only E. felidis) and Tsavo West (only E. granulosus). Host species identification for environmental faecal samples, based on field signs, was found to be unreliable. All samples with taeniid eggs were subjected to a confirmatory host species RLFP-PCR of the cytochrome B gene. 60% had been correctly identified in the field. Frequently, hyena faeces were mistaken for lion and vice versa, and none of the samples from jackals and wild dogs could be confirmed in the tested sub-sample. This is the first molecular study on the distribution of Echinococcus spp. in Kenyan wildlife. The presence of E. felidis is confirmed for lions and newly reported for spotted hyenas. Lions and hyenas are newly recognized hosts for E. granulosus s.s., while the role of leopards remains uncertain. These data provide the basis for further studies on the lifecycles and the possible link between wild and domestic cycles of cystic echinococcosis in eastern Africa.

Prevalence and genotyping of Echinococcus granulosus in sheep in Narok County, Kenya

Cystic echinococcosis (CE) is a zoonotic disease caused by the larval stage of Echinococcus granulosus species (sensu lato, s.l.). In East Africa, several species/strains occur in livestock, wildlife, and humans, but there is limited information on frequencies of infection by different genotypes in the various mammalian hosts. We have obtained data on E. granulosus infection prevalence in sheep sampled from abattoirs in Narok County, southern Kenya. We inspected carcasses for the presence of hydatid cysts in 180 sheep randomly selected in five sub-locations. The overall prevalence was 16.0% (144/900 animals), with the majority of cysts (50.7%) found in the liver, followed by the lungs (36.8%), while infections involving the liver and lungs were detected in 12.5% of the sheep. PCR–RFLP genotyping of the mitochondrial nad-1 gene in all the 343 cysts identified E. granulosus G1–G3 (sensu stricto, s.s.) as the only genotype. The majority of the cysts (62.1%) were fertile, and 35.2% were sterile, while 2.7% were calcified. Considering cyst fertility, 73.02% of lung cysts were fertile compared to 53.4% in liver cysts. Our data extends previous CE studies in livestock and indicates a high level of CE infection of sheep in Narok, with a predominance of E. granulosus s.s., which is highly pathogenic and commonly infects humans. Given the high fertility rates observed in the cysts, there is an urgent need to determine whether there is a significant incidence of human infection in Narok, and initiate “One Health” control measures.

Cystic echinococcosis in Turkana, Kenya: 30 years of imaging in an endemic region

Cystic echinococcosis (CE), a widespread, complex zoonosis, causes chronic disease associated with high morbidity. The pastoral Turkana people of Kenya have one of the highest prevalence rates of CE in the world. Between 1983 and 2015, a CE control program in the Turkana region used ultrasound (US) screening surveys and surgical outreach visits to evaluate CE prevalence and treat those with the disease. As the gold standard modality for diagnosing CE, US reveals a great deal of information about the disease in affected populations. The aim of this study is to discuss the characteristics of untreated CE in the Turkana people as revealed by US data collected during the CE control program and evaluate disease presentation, factors influencing the risk of transmission, and the timeline of disease progression. Data were obtained from written patient notes from US screenings and images; cysts were classified using the World Health Organization (WHO) standardized US classification of CE. Findings include greater prevalence of cysts, later stages of cysts, and multiple cysts in older age groups, with no multiple cysts occurring in patients under six years of age, which are consistent with the assertion that rates of exposure, transmission, and infection increase with age in endemic regions. Findings also raise questions regarding the timeline of disease progression, and factors potentially influencing disease transmission within this and other endemic populations. A comprehensive survey focusing on cultural and community observations (e.g., changing behaviors, hygienic practices, etc.) may provide more detailed information regarding factors that facilitate transmission.