Cerebral cystic echinococcosis in Mongolian children caused by Echinococcus canadensis

Primary cerebral cystic echinococcosis in a child from Roman countryside: Source attribution and scoping review of cases from the literature

BACKGROUND

Human cystic echinococcosis (CE) is a zoonotic parasitic infection caused by the larval stage of the species belonging to the Echinococcus granulosus sensu lato (s.l.) complex. Parasitic cysts causing human CE are mainly localized in the liver and in the lungs. In a smaller number of cases, larvae may establish in any organ or tissue, including the central nervous system (CNS). Cerebral CE (CCE) is rare but poses serious clinical challenges.

METHODS

This study presents a case of CCE in a child living in the countryside near Rome (Italy), along with a comparative molecular analysis of the isolated cyst specimens from the patient and sheep of local farms. We also systematically searched the literature to summarize the most relevant epidemiological and clinical aspects of this uncommon localization.

FINDINGS

The comparative molecular analysis confirmed that the infection was caused by E. granulosus sensu stricto (s.s.) (G3 genotype), and most likely acquired in the family farm. The literature search identified 2,238 cases of CCE. In 80.51% of cases, brain was the only localization and single CCE cysts were present in 84.07% of cases. Mean patients' age was 20 years and 70.46% were children. Cyst rupture was reported in 12.96% and recurrence of CCE after treatment in 9.61% of cases. Permanent disability was reported in 7.86% of cases, while death occurred in 6.21%. In case series reporting all CE localization, CCE represented 1.5% of all CE cases. In the few reports that identified at molecular level the CCE cyst, E. granulosus s.s. was found in 40% and E. canadensis in 60% of cases.

CONCLUSIONS

We report a rare case of CCE and evidenced the probable local origin of infection. The proportions of CE cases with uncommon localizations and with high impact on patients' lives have been globally neglected and should be included in the computation of the global burden of CE.

Prevalence and risk factors associated with human cystic echinococcosis in rural areas, Mongolia

Cystic echinococcosis is a chronic, complex and neglected zoonotic disease with considerable socio-economic impact on the affected population. Even though Mongolia is included in the list of high cystic echinococcosis risk countries, there has been very limited research and evidence on the prevalence or prevention of cystic echinococcosis. This field-based cross-sectional study to investigate the prevalence of cystic echinococcosis and its potential risk factors in Mongolia was conducted from April 2016 to March 2018. A total of 1,993 people were examined by ultrasound in five provinces of Mongolia. All cystic echinococcosis positive cases were classified according to the WHO-IWGE expert recommendations. The logistic regression model was used to detect the association between the presence of echinococcus infection and each potential risk factor. This was the first community survey based on ultrasound screening in Mongolia. We found 98 cystic echinococcosis cases (prevalence = 4.9%), including 85 abdominal ultrasound cystic echinococcosis positive cases and 13 abdominal ultrasound cystic echinococcosis negative cases (surgically treated cystic echinococcosis cases 11, and 2 confirmed cases of lung cystic echinococcosis by chestcomputed tomography in hospital of Ulaanbaatar). The prevalence of cystic echinococcosis varied greatly among different provinces, ranging from 2.0% to 13.1%. Children, elderly people and those with lower education had higher chances of getting cystic echinococcosis. Rather than dog ownership itself, daily practice for cleaning dog feces was associated with increased odds of cystic echinococcosis. The results of the present study show very high endemicity of cystic echinococcosis in Umnugovi province. Evaluation of potential risk factors associated with cystic echinococcosisshow high significance for following factors: demographics (age), social condition (education level) and hygiene practices (cleaning dog feces and use of gloves). Children under 18 and elderly people are considered as the most risk age groups in Mongolia.

A multiplex PCR for the identification of Echinococcus multilocularis, E. granulosus sensu stricto and E. canadensis that infect human

Echinococcus granulosus sensu stricto (s.s.), Echinococcus multilocularis and Echinococcus canadensis are the common causes of human echinococcosis in China. An accurate species identification tool for human echinococcosis is needed as the treatments and prognosis are different among species. The present work demonstrates a method for the simultaneous detection of these three Echinococcus species based on multiplex polymerase chain reaction (mPCR). Specific primers of this mPCR were designed based on the mitochondrial genes and determined by extensive tests. The method can successfully detect either separated or mixed target species, and generate expected amplicons of distinct size for each species. Sensitivity of the method was tested by serially diluted DNA, showing a detection threshold as less as 0.32 pg for both E. granulosus s.s. and E. canadensis, and 1.6 pg for E. multilocularis. Specificity assessed against 18 other parasites was found to be 100% except weakly cross-react with E. shiquicus. The assay was additionally applied to 69 echinococcosis patients and 38 healthy persons, confirming the high reliability of the method. Thus, the mPCR described here has high application potential for clinical identification purposes, and can further provide a useful tool for evaluation of serology and imaging method.

Genotyping and phylogenetic analysis of unusually located hydatid cysts isolated from humans in north-east Iran

Despite several studies conducted to determine the genotypes of cystic echinococcosis (CE) agents in humans and other intermediate hosts, the relationship between parasite genotype and clinical presentation of hydatidosis is yet to be well defined. The aim of this study was to compare the genotypes/haplotypes of CE agents of human extra-hepatopulmonary hydatid cysts and common hydatid cysts of the liver. A comparative analysis was carried out between partial cox1 sequences of ten extra-hepatopulmonary hydatid cysts, two liver cysts and reliable sequences from the GenBank database. All the studied hydatid cysts had the Echinococcus granulosus sensu stricto (G1-G2-G3) genotypes. The liver CE cysts were caused by common G1 genotype, while six of the extra-hepatopulmonary cysts had genotypes different from common G1 cysts. The sequences of these six isolates were identical to the G2 and G3 genotypes of E. granulosus sensu stricto; the kidney and peritoneum cysts and most of the brain cysts were identified as G2 genotype, while G3 genotype was only reported in a cyst belonging to the pelvic region. Given the observed differences between the sequences of hydatid cysts, it seems that the replacement of hydatid cysts in organs other than the liver and lungs can be related to their genotypes and probably intra-genotypic characteristics. It was hypothesized that in each geographic area, less frequent genotypes were likely to be more consistent with placement in the host's unusual organs.

Evidence for camels (Camelus bactrianus) as the main intermediate host of Echinococcus granulosus sensu lato G6/G7 in Mongolia

Cystic echinococcosis (CE), the parasitic disease caused by the larval stage of Echinococcus granulosus sensu lato (s.l.), is a global public health problem. In Mongolia, despite wide distribution of human CE, not enough information is available on the prevalence and molecular characterization of CE in livestock and its zoonotic linkage with human cases. We investigated the distribution of human CE cases and livestock population using statistical models to get insight into the zoonotic linkage. The incidence of human CE cases increased by a factor of 1.71 for one interquartile range increment in the density of the camel population. No significant association was observed with other livestock species. The samples collected from 96 camels and 15 goats in an endemic region showed a CE prevalence of 19.7% and 6.7%, respectively. All livestock CE were E. granulosus s.l. G6/G7 species of the E. granulosus s.l. complex. The genetic diversity was investigated using the haplotype network based on full cox1 gene analysis of the samples collected from livestock CE and nucleotide sequences previously reported from human CE and wild canids infection in Mongolia. Four haplotypes were identified within the livestock samples, two of which had not been previously reported. A common haplotype was identified among humans, camels, goats, and a wolf, all of which were within the same geographical area. A mixed infection of E. granulosus s.l. G6/G7 with different haplotypes in the intermediate host was identified. To the best of our knowledge, this is the most comprehensive description of the current epidemiological situation of CE in Mongolia with substantial evidence that camels might be the main intermediate host of E. granulosus s.l. G6/G7 in Mongolia. Moreover, our result presents the first report in the country to provide insight into the prevalence of E. granulosus s.l. G6/G7 in livestock.