Epidemiology, treatment and follow-up of human echinococcosis on the eastern Tibetan Plateau, China

Li, T 2010, Epidemiology, treatment and follow-up of human echinococcosis on the eastern Tibetan Plateau, China , PhD thesis, Salford : University of Salford.

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Abstract

The current study aimed to determine the prevalence of human echinococcosis in Tibetan communities of Sichuan Province, undertake genotyping of human echinococcosis isolates from the Tibetan Plateau, and assess the clinical efficacy of albendazole in human cystic and alveolar echinococcosis. In addition, specific IgG serologic responses against recombinant antigens (AgB and Em 18) were also examined in Tibetan cystic and alveolar echinococcosis patients. Abdominal ultrasound screening programmes for echinococcosis were conducted in 31 Tibetan townships in Ganze and Aba Tibetan Autonomous Prefectures of northwest Sichuan Province during 2001-2008. Hospital records (1992-2006) in a major regional treatment centre for echinococcosis in Aba Prefecture were also reviewed. Of 10.186 local residents examined by portable ultrasound scan, 645 (6.3%) were diagnosed with echinococcosis: a prevalence of 3.2% for cystic echinococcosis (CE), 3.1% for alveolar echinococcosis (AE) and 0.04% for dual infection (both CE and AE). Further analysis revealed that human cystic and alveolar echinococcosis in pastoral areas was highly co-endemic, in comparison to much lower human prevalences found in semi-pastoral or farming regions. The high ultrasound prevalence of hepatic echinococcosis in these co-endemic areas in northwest Sichuan Province was also reflected in the hospital study, and hospital records furthermore indicated another possibly highly co-endemic transmission focus in Guoluo Prefecture of Qinghai Province, located at the border of northwest Sichuan. Parasite isolates from 68 human cases originating from Sichuan and Qinghai provinces in eastern China were postoperatively examined by histopathology and PCR-RFLP for specific identification of Echinococcus spp. Histopathologically, 38 human isolates were confirmed as E. granulosus and 30 as E. multilocularis. PCR-RFLP with rrnL as the target gene confirmed 33 of 53 of the isolates to have the Gl genotype of sheep/dog strain of E. granulosus as the only source of infection, while the remaining 20 were confirmed as E. multilocularis. No human infections were shown to be caused by E. shiquicus which is also endemic in wildlife hosts in the region. Specific IgG responses to recombinant antigen B and Eml8 in ELISA were examined in 422 ultrasound-detected echinococcosis patients, including 246 with CE, 173 with AE, and 3· with dual infection. As a result, rAgB-specific antibody was detected in 77.6% of CE and 86.1% of AE cases, while rEmlS-specific antibody was present in 28.9% of CE and 87.3% of AE patients. All three patients with dual infection exhibited specific antibodies responding to rAgB and rEml8. Further analysis revealed that rAgB-specific antibody was elevated in a significantly greater proportion (87.3%) of CE patients with cysts at active or transitional stages (CE1, CE2 or CE3), compared to 54.8% of other patients with cysts at an early or an inactive stage (CL or CE4 or CE5). Additionally, rAgB-specific antibody was detected in 95.6% of CE2 cases, which was statistically greater than that (73.7%) in CE1 patients. Although rEmlS-specific antibody was elevated in 28.9% of CE patients, the positive reaction was much weaker in CE than in AE cases. Serum levels and concentrations of rEmlS-specific antibody were further indicated to be strongly disease phase correlated in AE patients, with positive rates of 97.4% in cases with alveolar lesions containing central necrosis and 66.7% in patients with early alveolar lesions that measured <5 cm. Efficacies of cyclic albendazole treatment were longitudinally assessed in 49 CE patients using ultrasonography and ELISA with rAgB as antigen. Of these 49 cases, 32.7% (16) were considered to be cured by ultrasound, 49.0% (24) were improved, 14.3% remained unchanged, whereas 4.1% were aggravated. Based on rAgB in ELISA, IgG4 was indicated to be the most predominant IgG subclass in serum of CE patients. However, the changes of specific antibodies (IgG and IgG4) were poorly correlated with the outcomes of treatment. Even so, positive antibody seroconversion (IgG and IgG4 antibodies) in patients who were originally seronegative, and simultaneous observation of detachment of cyst membrane and/or partial degeneration of cyst content occurred in 46.2% (6/13) of CE1 patients after 6-12 months chemotherapy. In 28 AE patients following cyclic albendazole therapy (mean course = 23.4 months), ultrasound examination indicated that 25 (89.3%) had static alveolar lesions, whereas 3 (10.7%) had aggravated disease. In response to rEml8, IgG4 was the predominant IgG subclass in AE cases, and it was broadly correlated with the outcomes of treatment. In conclusion, human cystic and alveolar echinococcosis proved to be highly co-endemic in pastoral areas of Tibetan communities of Sichuan Province, with the Gl genotype of E. gmnulosus as the only identified source of human CE infection. Recombinant AgB proved to be highly useful for serodiagnosis of human echinococcosis, whereas rEmlS was more species-specific in differential diagnosis of human AE. Cyclic albendazole therapy was effective for treatment of human CE and AE. The changes of specific antibody against rAgB were poorly correlated with the outcomes of treatment in CE patients, whereas serum concentrations of rEmlS-specific antibody were strongly correlated with parasite activities in AE cases.

Item Type:	Thesis (PhD)
Contributors:	Craig, PA (Supervisor)
Schools:	Schools > School of Environment and Life Sciences
Depositing User:	Institutional Repository
Date Deposited:	03 Oct 2012 13:34
Last Modified:	04 Aug 2022 11:25
URI:	https://usir.salford.ac.uk/id/eprint/26772

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