Study On The Leishimania Infection In Human And Domesticated Animals In The Desert-type Kala-azar Endemic Areas In Xinjiang

BackgroundDesert-type kala-azar was caused by Leishmania infantum which was transmitted by sandfly. The patients are mainly infants under 2 years old. The endemic areas are distributed in desert areas of the northern margin of Tarim Basin in Xinjiang and in Mesozoic-Cenozoic of Inner Mongolia. Since the vertebrate reservoir host is still unknown, the best strategy for leishmaniasis control is the treatment for the patients, leishmaniasis remains a serious health problem for the infants in these areas.ObjectiveThis study is to clarify the characteristics of the desert-type kala-azar, especially the infection in human and domesticated animals and explore the potential vertebrate hosts in this area in order to understand their roles in the transmission of the disease.MethodsIn April 2014, the blood of the leishmaniasis patients, their family members and domesticated animals were collected in the study township, Jiashi County, Xinjiang, a desert type endemic area for leishmaniasis. The ribosomal internal transcribed spacer (ITS-1) was selected as the target gene and a nested PCR was carried out to detect the specific DNA fragments of Leishmania in the blood of the subjects. The results of the tests were analyzed statistically. The nPCR amplified products were sequenced at first, and then the restriction fragment length polymorphism (RFLP) and homology comparison were performed. For the liver and spleen of the domesticated animals, these tissues were imprinted and examined microscopically. The human blood and some tissues of the liver and spleen of the domesticated animals were cultured in NNN’s medium.ResultsThe positive rate of nPCR in human was 88.18%(97/110). The positive rates had no significant difference between sex, the patients and their family members. A total of 118 animals were detected by rk39 and nPCR test in the study. The positive rates of rk39 and nPCR was 19.49%(23/118) and 54.24%(64/118), respectively. The positive rates of rk39 and nPCR had no significant difference between sex, the local sheep and the exotic sheep. The positive rates at different ages did not showed a linear trend. The positive rates of nPCR was higher than that in rk39 test(X2=41.0, P<0.05). It was thought the parasite detected in the sheep and the patients was Leishmia infantum. However, the results of the microscopy examination and the cultivation were negative.ConclusionThe asytomatic and the domesticated animals may be the host of Leishmania infantum in desert-type kala-azar endemic area. Further study in a wide scope is recommended in order to make clear the role of asymptomatic and domesticated animals in the transmission of leishmaniasis in the study area.