Determinants of Campylobacter species diversity in infants and association with family members, livestock, and household environments in rural Eastern Ethiopia.

Background infections pose a significant challenge in low- and middle-income countries, contributing to child mortality. is linked to acute gastrointestinal illness and severe long-term consequences, including environmental enteric dysfunction (EED) and stunting. In 2018, our cross-sectional study in Ethiopia detected in 88% of stools from children aged 12-15 months, with an average of 11 species per stool using meta-total RNA sequencing. Building on these findings, we conducted a longitudinal study (December 2020-June 2022) to investigate colonization of infants and identify reservoirs and risk factors in rural eastern Ethiopia. Results After a preliminary screening of 15 species using species-specific quantitative PCR, we analyzed four target species in 2,045 samples from infants (first month to just one year of life) and biannual samples from mothers, siblings, and livestock (goats, cattle, sheep, and chickens). C. infans (41%), (26%), and (13%) were identified as the predominant in the infant gut. Colonization of and increased ( : 0.85%, -0.98% increase/ day in the odds of colonization) and abundance (P = 0.027, 0.024) with age. Enteric symptoms were strongly associated with (diarrhea: OR = 2.02 [95%CI: 35%,100%]; fever: OR = 1.62 [95%CI: 14%, 83%]) and (diarrhea: OR = 2.29 [95%CI: 46%,100%], fever: OR = 2.53 [95%CI: 56%,100%]). Based on linear mixed models, we found elevated cumulative loads of load in infants (especially females OR = 1.5 [95%CI: 10%, 67%]), consuming raw milk (OR = 2.3 [95%CI: 24%,100%]) or those exposed to areas contaminated with animal droppings (OR = 1.6 [95%CI: 7%,93%]), while cumulative loads were higher in infants ingesting soil or animal feces (OR = 2.2 [95%CI: 23%,100%]). was also prevalent in siblings (56%) and mothers (45%), whereas was common in chickens (38%) and small ruminants (goats 27%, sheep 21%). Conclusions was highly prevalent in rural Ethiopian infants. was primarily associated with human hosts, and was mainly linked to zoonotic sources. Our findings emphasize the need for targeted interventions addressing environmental, dietary, and behavioral factors to reduce transmission in resource-limited settings.