Gastrointestinal (GI) parasitic infections in non-human primates are of growing concern due to their implications for both veterinary and public health. Long-tailed macaques (Macaca fascicularis), commonly found in peri-urban and temple environments in Southeast Asia, may act as reservoirs for zoonotic parasites, posing risks to humans and domestic animals. This study investigated the prevalence and species diversity of GI parasites in free-ranging macaques from four provinces in Northeast Thailand (Loei, Khon Kaen, Bueng Kan, and Sisaket). A cross-sectional study was conducted between April and May 2025. A total of 445 fecal samples were examined using two parasitological techniques: agar plate culture (APC) and the formalin–ethyl acetate concentration technique (FECT). The overall prevalence of parasitic infection was 86.5%, with Strongyloides sp. (65.2%) as the most prevalent helminth and Balantioides coli-like (29.5%) and Entamoeba histolytica-like (28.8%) as the predominant protozoa. Other parasites identified included helminths (Trichuris sp., Ascaris sp.) and protozoa (Blastocystis sp., Iodamoeba bütschlii, Entamoeba coli, and Chilomastix mesnili). Mixed infections were frequently observed, with both helminths and protozoa co-occurring in 37.3% of cases. The high infection rates and parasite diversity reflect substantial environmental contamination and sustained transmission cycles. These findings underscore the importance of integrated surveillance in wildlife populations and the need for One Health-based approaches to minimize zoonotic transmission risks at the human–animal–environment interface.

The increasing resistance to chemical pediculicides has raised concerns about the efficacy of head lice treatments, including in Thailand. This study evaluated the efficacy of three commercially available pediculicide shampoos (0.75% permethrin, 0.6% carbaryl, and 0.12% Stemona root crude extract) among infested children in Chonburi Province, Thailand. A pre-test/post-test experimental design was conducted with 135 infested female children assigned to three treatment groups (n = 45 each), with no significant differences in baseline demographic characteristics (level of head lice infestations, hairstyle, and hair length). Each group received two applications (Day 0 and Day 7) of the allocated pediculicide shampoo, following the manufacturer’s instructions. The final proportion of cured individuals was assessed on Day 14 after treatment using a fine-tooth comb. The observed percentages of cured individuals were 42.22% for carbaryl shampoo, 24.44% for Stemona shampoo, and 6.67% for permethrin shampoo. No side effects were reported, although none of the shampoos achieved complete eradication, with particularly poor outcomes in children with heavy infestations. These findings provide clinical evidence of reduced efficacy of over-the-counter pediculicides in Thailand, consistent with emerging resistance trends. More effective alternatives with different mechanisms of action, including ivermectin, abametapir, and dimeticone-based products, should be considered, although their current availability in Thailand remains limited. In the interim, development of locally available herbal formulations, together with school-based screening and simultaneous treatment, represents more feasible strategies. These results highlight the need for updated treatment guidelines, restriction of ineffective products, and regular resistance surveillance to ensure effective control.

Pediculosis remains a public health problem among primary schoolchildren worldwide, including in Thailand. This study aimed to determine the prevalence of pediculosis and identify associated determinants among primary schoolgirls from different socio-geographic regions of Thailand to inform effective control strategies. A cross-sectional survey was conducted among 494 schoolgirls from eastern, northeastern, and southern provinces. Data on demographic characteristics, socioeconomic status, personal hygiene practices, parental knowledge and attitudes toward head lice, and school health policies were collected using questionnaires and interviews with school administrators. Univariable analyses and a generalized linear mixed model (GLMM) with school as a random effect were used to account for clustering. The overall prevalence of pediculosis was 50.81% (95% CI: 46.31–55.20), with significant variation across provinces. In univariable analysis, several factors were associated with infestation. However, after accounting for clustering, only class level (adjusted OR = 3.09; 95% CI: 1.31–7.29) and self-performed hair washing (adjusted OR = 2.93; 95% CI: 1.57–5.49) remained significantly associated with pediculosis, while other associations were attenuated. Parental knowledge was moderate, and commonly held beliefs regarding prevention and treatment varied. None of the participating schools had routine head lice screening policies. These findings indicate that pediculosis is likely influenced by both individual and school-level factors. Control efforts may benefit from coordinated school-based approaches, alongside improved access to effective treatment and targeted health education.

Head louse infestation (Pediculosis humanus capitis) remains a common public health problem among school-aged children. While reduced efficacy of pediculic