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Am J Trop Med Hyg
Am J Trop Med Hyg
tpmd
tropmed
The American Journal of Tropical Medicine and Hygiene
0002-9637
1476-1645
The American Society of Tropical Medicine and Hygiene

tpmd240259
10.4269/ajtmh.24-0259
Letter to the Editor
Ivermectin Treatment for Strongyloidiasis in Thailand
Hokama Akira 1
Department of Medical Checkup Naha City Hospital Naha, Okinawa, Japan E-mail: hokamaakira@gmail.com

2 7 2024
9 2024
2 7 2024
111 3 703703
© 2024, The author(s)
2024
https://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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pmcDear Sir,

I read with interest the article “High Efficacy of Ivermectin for Strongyloidiasis Treatment,” which described how a single dose of ivermectin (200 μg/kg) successfully eliminated Strongyloides stercoralis infection in asymptomatic individuals in northeast Thailand, with a 100% cure rate.1 I congratulate the authors on their efforts and fully agree with their highlighting ivermectin as a primary treatment of strongyloidiasis in an endemic community. I would like to comment on the possible reasons why they have achieved a 100% cure rate. It is well known that co-infection with human T-cell lymphotropic virus type 1 (HTLV-1) has been associated with a high rate of strongyloidiasis treatment failure.2,3 Hyperinfection syndrome and disseminated strongyloidiasis frequently occur with HTLV-1 co-infection,2 resulting in a high mortality rate despite repeated administration of ivermectin. In a prior study treatment with ivermectin (200 μg/kg twice) for strongyloidiasis led to parasite clearance in 100% (42/42) of patients without HTLV-1 co-infection, whereas it was 90% (18/20) in those with the co-infection.4 A large scale serological survey affirmed that HTLV has not been endemic in Thailand.5 I therefore speculate, that although the virological backgrounds of the volunteers were not described, the non-endemic status of HTLV-1 contributed to the 100% cure rate in the new study. Co-infection with another immunocompromising factor, human immunodeficiency virus (HIV), has been a serious healthcare problem in Asia,6 and the efficacy of ivermectin against strongyloidiasis has not been evaluated for asymptomatic individuals with HIV infection. In conclusion, although the new study provides valuable information on ivermectin treatment for asymptomatic strongyloidiasis, future research, including consideration of virological backgrounds, is needed before concluding that single-dose ivermectin treatment is sufficient for asymptomatic strongyloidiasis in Thailand.
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REFERENCES

1. Sengthong C Pinlaor S Yingklang M Haonon O Jantawong C Pinlaor P Sithithaworn P Hongsrichan N , 2024. High efficacy of ivermectin for strongyloidiasis treatment. Am J Trop Med Hyg 110 : 951–952.38579698
2. Ye L Taylor GP Rosadas C , 2022. Human T-cell lymphotropic virus type 1 and Strongyloides stercoralis o-infection: A systematic review and meta-analysis. Front Med (Lausanne) 9 : 832430.35237633
3. Hirata T Uchima N Kishimoto K Zaha O Kinjo N Hokama A Sakugawa H Kinjo F Fujita J , 2006. Impairment of host immune response against Strongyloides stercoralis by human T cell lymphotropic virus type 1 infection. Am J Trop Med Hyg 74 : 246–249.16474078
4. Zaha O Hirata T Uchima N Kinjo F Saito A , 2004. Comparison of anthelmintic effects of two doses of ivermectin on intestinal strongyloidiasis in patients negative or positive for anti-HTLV-1 antibody. J Infect Chemother 10 : 348–351.15614460
5. Oota S Chaiwong K Pikulsod S Khuenkaew R Pheakkhuntod S Rattajak P Kramkratok P Shiu C Bhatnagar S Sakuldamrongpanich T , 2018. Human T-cell lymphotropic virus type I and II seroprevalence among volunteer blood donors in Thailand. Pathog Glob Health 112 : 343–348.30424716
6. Akanksha K Kumari A Dutta O Prasanth A Deeba F Salam N , 2023. Prevalence of soil-transmitted helminth infections in HIV patients: A systematic review and meta-analysis. Sci Rep 13 : 11055.37422549
