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

Background: Campylobacter infections pose a significant challenge in low- and middle-income countries, contributing to child mortality. Campylobacter 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 Campylobacter 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 Campylobacter colonization of infants and identify reservoirs and risk factors in rural eastern Ethiopia. Results: After a preliminary screening of 15 Campylobacter species using species-specific quantitative PCR, we analyzed four target species in 2045 samples from infants (first month to just one year of life) and biannual samples from mothers, siblings, and livestock (goats, cattle, sheep, and chickens). Candidatus C. infans (41%), C. jejuni (26%), and C. upsaliensis (13%) were identified as the predominant in the infant gut. Colonization of C. infans and C.jejuni increased (C. infans: 0.85%, C. jejuni-0.98% increase/ day in the odds of colonization) and abundance (P = 0.027, 0.024) with age. Enteric symptoms were strongly associated with C. infans (diarrhea: OR = 2.02 [95%CI: 35%,100%]; fever: OR = 1.62 [95%CI: 14%, 83%]) and C. jejuni (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 C. infans 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 C. jejuni cumulative loads were higher in infants ingesting soil or animal feces (OR = 2.2 [95%CI: 23%,100%]). C. infans was also prevalent in siblings (56%) and mothers (45%), whereas C. jejuni was common in chickens (38%) and small ruminants (goats 27%, sheep 21%). Conclusions: Campylobacter was highly prevalent in rural Ethiopian infants. C. infans was primarily associated with human hosts, and C. jejuni was mainly linked to zoonotic sources. Our findings emphasize the need for targeted interventions addressing environmental, dietary, and behavioral factors to reduce Campylobacter transmission in resource-limited settings.