|SHORT RESEARCH COMMUNICATION
|Year : 2018 | Volume
| Issue : 3 | Page : 242-244
An investigation about the possible role of cattle and goats as reservoir hosts for Leishmania donovani in Bangladesh
Mohmmad Zahangir Alam, Md Mustafizur Rahman, Shirin Akter, Md Hasanuzzaman Talukder, Anita Rani Dey
Department of Parasitology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh
|Date of Submission||30-Nov-2017|
|Date of Acceptance||23-Feb-2018|
|Date of Web Publication||4-Jan-2019|
Department of Parasitology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh–2202
Source of Support: None, Conflict of Interest: None
Keywords: Bangladesh; reservoir; visceral leishmaniasis
|How to cite this article:|
Alam MZ, Rahman MM, Akter S, Talukder MH, Dey AR. An investigation about the possible role of cattle and goats as reservoir hosts for Leishmania donovani in Bangladesh. J Vector Borne Dis 2018;55:242-4
|How to cite this URL:|
Alam MZ, Rahman MM, Akter S, Talukder MH, Dey AR. An investigation about the possible role of cattle and goats as reservoir hosts for Leishmania donovani in Bangladesh. J Vector Borne Dis [serial online] 2018 [cited 2019 Mar 26];55:242-4. Available from: http://www.jvbd.org/text.asp?2018/55/3/242/249484
Visceral leishmaniasis (VL), an important tropical disease, is caused by the intracellular protozoan parasites of the Leishmania donovani complex. VL is a serious public health problem in the Indian subcontinent, and there are 40,000–45,000 cases per year in Bangladesh. VL, caused by L. infantum (synonym L. chagasi) is a zoonotic disease, and is distributed mainly in Mediterranean countries, the Middle East, Asia, and South America; with canine and other mammalian species acting as reservoir hosts,. Transmission of VL caused by L. donovani is still considered to be anthroponotic in the Indian Subcontinent although the only known vector, Phlebotomus argentipes is zoophilic in nature. Earlier studies have shown that P. argentipes prefer to feed on both bovine and human blood,. In India, the cattle density is considered as one of the risk factors for the increased number of VL cases in human. Anti-L. donovani antibodies has been detected in different domestic animals including cattle in eastern Sudan. In Nepal, Leishmania DNA has been detected in cows, buffaloes and goats and recently in goats in India. These reports support the hypothesis of an animal reservoir for VL transmission in Bangladesh.
Studies investigating the role of domestic animals as reservoir of VL in Bangladesh are limited. In a recent study, Leishmania infection in stray dogs in VL-endemic areas of Bangladesh was detected by serological and molecular tests. Anti-Leishmania antibodies were detected in cattle from an endemic area in Bangladesh, but no parasitic DNA was detected by PCR. Literature search did not reveal any earlier study in Bangladesh investigating the domestic goats for the presence of Leishmania infection. Traditionally, cattle and goats are kept very close to or within the human households, and therefore, it is possible that they are frequently bitten by the vector sandflies. Therefore, it is important to study the possible role of domestic animals in VL epidemiology. This study was aimed to investigate the probable role of cattle and goats as reservoir hosts for L. donovani in a VL-endemic area of Bangladesh.
Venous blood (5 ml) was collected in tubes containing disodium ethylenediaminetetraacetate (Na2 EDTA) from 258 cattle and 122 goats in Trishal and Fulbaria Upazila (subdistricts) of Mymensingh district in Bangladesh, which are the two most endemic areas for VL. The samples were immediately kept in a chilled ice box and transferred to the Department of Parasitology, Bangladesh Agricultural University, Mymensingh, Bangladesh. The blood samples were centrifuged at 875 × g for 10 min at 4°C and serum samples were also stored at 4°C. Buffy coat samples were stored in lysis buffer for DNA isolation. As there is no established central ethical committee on animal experimentation in Bangladesh, blood samples were collected after establishing collaborations with local veterinarians and with consent from the animal owners.
Separated sera samples were used for rK39 immunochromatographic (ICT) test (InBios International, Inc., Seattle, WA, USA) according to the manufacturer's instructions. In positive cases two bands—A positive test band and the control band appeared on the test strip, within 5 min. Appearance of only the control band was indicative of negative for rK39 test.
DNA was extracted from the buffy coat of all the samples by using the DNeasy blood and tissue kit (Qiagen, Germany) according to manufacturer's instructions.
ITS1-PCR assays were performed to amplify the internal transcribed spacer 1 (ITS1) region in the ribosomal operation using the primers LITSR (5'-CTG GAT CAT TTT CCG ATG-3') and L5.8S (5'-TGA TAC CAC TTA TCG CAC TT-3'). The amplification cycles included initial heating at 95°C for 2 min, followed by 35 cycles consisting of denaturation at 95°C for 20 sec, annealing at 53°C for 30 sec and extension at 72°C for 1 min, with a final extension step at 72°C for 6 min. PCR products were resolved by 1.5% agarose gel electrophoresis in 1×Tris-Borate-EDTA buffer and visualized using UV light after staining with RedSafe Nucleic Acid Staining Solution (iNtRON Biotechnology Inc., Sungnum, Korea). A positive control with L. donovani genomic DNA and a negative control with no-DNA water were included.
Anti-Leishmania antibodies was detected in 18 samples (10 cattle and 8 goats) out of 380 (4.73%) in rK39 ICT dipstick test [Figure 1]. None of the seropositive and seronegative samples was found positive for the detection of Leishmania DNA by ITS1-PCR.
|Figure 1: rK39 immunochromatographic strip test results. Strips with only the control band represent negative results, while strip with both a control band and a positive test band (arrow marked) reflect positive results.|
Click here to view
Although the transmission of VL between domestic animals and human is a great concern, information on the VL infection in animals in the subcontinent is lacking. The possible role of domestic animals in the transmission of anthroponotic VL has been previously studied in Bangladesh, but the role of animals as risk factors or reservoir hosts was not established.
The detection of anti-Leishmania antibodies but not Leishmania DNA in cattle in this study corroborate with the findings of previous study by Alam et al. In Sudan, screening of several domestic animals with the direct agglutination test (DAT) detected reaction rates above the cut-off titres in donkeys (68·7%), cows (21·4%), goats (8·5%), and wild rats (5·5%). In another recent study in India, L. donovani DNA was detected in 20 rK39 positive blood samples from goats and one sample from a cow indicating that goats are potential animal reservoirs of human VL in that area.
In the present study, no evidence of Leishmania DNA was found by ITS1-PCR in seropositive and seronegative cattle and goat samples. Here, we used buffy coat for DNA extraction, which is the third most convenient sample after spleen and bone marrow, but preferred in this study as collection of whole blood is less invasive, repeatable and easily accepted by dog owners. Therefore, aliquots of buffy coat may not have enough Leishmania DNA to be amplified by ITS1-PCR and even the sensitivity of ITS1-PCR in previous studies was not found 100%,. Furthermore, cross-reacting antibodies inferred by other infections might result in antibody responses in the cattle and goats. Earlier studies demonstrated that anti-Leishmania antibodies can be cross-reactive with tuberculosis, toxoplasmosis, and malaria for human sera,. However, this study did not investigate such cross-reactivity.
The absence of Leishmania DNA is suggestive of no role of cattle and goats as reservoirs of VL in this endemic focus. However, further detailed studies are recommended to reveal the potential role of other domestic and wild animals on which sandflies feed in the VL epidemiology in Bangladesh.
Conflict of interest
The authors declare no conflict of interest.
| Acknowledgements|| |
The study was supported by the Ministry of Science and Technology of Bangladesh (Project No. BS. 23, 2014–2015).
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