Human fascioliasis and the presence of hybrid/introgressed forms of Fasciola hepatica and Fasciola gigantica in Vietnam.

The two species common of liver fluke, Fasciola hepatica and Fasciola gigantica, cause human fascioliasis. Hybrids between these species, and introgressed forms of Fasciola, are known from temperate and subtropical regions of eastern Asia. Here, we report the presence of hybrid and/or introgressed liver flukes in Vietnam where it has recently been recognised that human fascioliasis is an important zoonotic disease. Specimens examined came from domestic stock (cattle and buffalo) at slaughter and also from human patients. DNA sequences were obtained from the nuclear ribosomal second internal transcribed spacer (ITS-2) and from portions of two mitochondrial protein-coding genes. Mitochondrial sequences in every case were similar to those of Fasciola gigantica. Nuclear ITS-2 sequences belonged to one or other of the Fasciola species, or, sequences from both were found in the same individual worm. This study extends the known range of hybrids or introgressed forms of Fasciola into tropical regions of Asia.

Diagnostic value of the recombinant tandem repeat antigen TeGM6-4r for surra in water buffaloes.

Trypanosoma evansi infection, or surra, is currently affecting various species of animals, especially water buffaloes. Since diagnosis is an important aspect of surra control, development of novel diagnostic antigens is of interest to implement and improve the currently utilized methods. Our study evaluated the tandem repeat antigen TeGM6-4r in T. evansi antibody detection in water buffaloes. TeGM6-4r-based ELISA was performed with 20 positive and 8 negative controls and 484 field samples from water buffaloes in Northern Vietnam. To examine cross-reactivity, sera from Japanese cattle that had been experimentally infected with Theileria orientalis (n=10), Babesia bovis (n=3), Babesia bigemina (n=7) and Trypanosoma theileri (n=59) were included in the study. The sensitivity of the test was 80%. TeGM6-4r did not react with Theileria or Babesia infected sera, however it showed cross reactivity with 11/59 T. theileri infected samples. The reference test, CATT/T. evansi also reacted with 3/59 T. theileri infected sera. The lysate antigen-based ELISA reacted with 4/59 T. theileri, 9/10 Theileria and 3/10 Babesia infected sera. In contrast, TeGM6-4r-based ELISA was 86.3% sensitive and 58.3% specific in the screening of field samples. The average seroprevalence of T. evansi infection among water buffaloes in Northern Vietnam was 27.1% by CATT/T. evansi and 53.7% by TeGM6-4r. Seroprevalence in the five surveyed provinces ranged from 17.4% to 39.8% in the reference test, and 47.3% to 67.3% in the recombinant antigen based test. The finding indicated that the disease is still widely endemic in the area and that surveillance programs need to be carried out regularly to better control surra. We proposed TeGM6-4r as a useful serodiagnostic antigen for the detection and epidemiological surveillance of T. evansi infection among water buffaloes.

Seroprevalence of Trypanosoma evansi infection in water buffaloes from the mountainous region of North Vietnam and effectiveness of trypanocidal drug treatment.

Water buffalo (WB) is an important domestic animal in Vietnam. This study utilized a card agglutination test to investigate seroprevalence of surra in WB population. Sera were collected from 585 WB from 4 different regions in Cao Bang and Thai Nguyen Provinces. Among them, 131 samples (22.4%) were positive for surra. The highest prevalence (24.6%) was found among 3 to 5 years old WB. Buffaloes less than 3 years old had the lowest prevalence (15.6%). Among 27 abortion cases, 9 WB (33.3%) were surra positive. For treatment of surra, Berenil® demonstrated a 100% cure rate, while that of Trypamidium® was only 40%. Our findings suggest that the current control strategy has not succeeded in reducing prevalence of surra in Vietnam.