Hidden Bacterial Pathogens Circulate Across Tunisian Ecosystems

A diverse array of bacterial pathogens and vector-associated microbes circulates across Tunisia, yet human disease surveillance remains largely compartmentalized from veterinary and environmental studies. Situated at the crossroads of the Mediterranean basin, North Africa, and the Sahara, the country encompasses diverse ecological zones that support a wide range of arthropod vectors and animal hosts. Over the past three decades, research teams have documented numerous zoonotic and suspected zoonotic bacteria, including species of Rickettsia, Bartonella, Anaplasma, Ehrlichia, Borrelia, and Coxiella. A comprehensive analysis published in Frontiers in Microbiology critically synthesizes this extensive body of literature to evaluate what current data actually demonstrate, where critical evidence gaps remain, and how a coordinated One Health approach can improve public health preparedness.

How Environmental Diversity Shapes Vector-Borne Circulation

The geographical heterogeneity of Tunisia creates distinct ecological niches that govern vector distribution and bacterial circulation. Northern humid and forested regions harbor tick species such as Ixodes ricinus and Ixodes inopinatus, which maintain cycles involving Lyme borreliosis group spirochetes and forest-associated rickettsiae. In contrast, semi-arid livestock areas and arid Saharan camel-rearing systems are dominated by ticks of the genus Hyalomma and soft ticks such as Ornithodoros erraticus. These vectors encounter diverse domestic and wild hosts, including sheep, goats, cattle, horses, dromedary camels, rodents, hedgehogs, and red foxes.

The authors emphasize that detecting bacterial DNA in an arthropod or animal host does not automatically prove biological vector competence or reservoir status. While molecular surveys have successfully expanded the catalog of detected taxa, many findings represent transient carriage, blood-meal remnants, or ecological associations rather than confirmed human health threats. Distinguishing between active infection, simple exposure, and environmental microbiome signals is essential for accurate epidemiological interpretation.

Dividing the Evidence Across Major Bacterial Groups

The review organizes existing findings into distinct taxonomic categories, each exhibiting a unique One Health profile:

• Rickettsia species: This group represents the most structured evidence base in Tunisia. While Mediterranean spotted fever caused by Rickettsia conorii remains the most clinically established rickettsiosis transmitted by the brown dog tick Rhipicephalus sanguineus, molecular methods have revealed broader species diversity. These include Rickettsia massiliae, Rickettsia aeschlimannii in camel-associated Hyalomma ticks, and Rickettsia felis associated with fleas.
• Bartonella species: Human data are largely driven by hospital-based cohorts identifying Bartonella quintana and Bartonella henselae as major etiological agents in blood culture-negative endocarditis cases. Veterinary and entomological studies have detected zoonotic Bartonella DNA in fleas collected from domestic and pastoral animals, as well as in dromedary camels and synanthropic rodents.
• Anaplasmataceae family: The evidence for Anaplasma is heavily animal- and tick-centered, featuring high prevalence of Anaplasma ovis in small ruminants and diverse strains such as Anaplasma phagocytophilum-like and Anaplasma platys-like genotypes. Conversely, human confirmation remains absent, and Ehrlichia evidence is largely restricted to canine seropositivity for Ehrlichia canis and sporadic wildlife detections.
• Borrelia species: Two distinct epidemiological cycles emerge. Northern humid zones feature the Borrelia burgdorferi complex, notably Borrelia lusitaniae maintained primarily through reptile-associated transmission involving the lizard Psammodromus algirus and Ixodes ticks. Southern arid regions harbor Borrelia crocidurae within Ornithodoros erraticus soft ticks inhabiting rodent burrows.
• Coxiella burnetii: Primarily recognized as a livestock-associated and environmentally transmitted pathogen responsible for Q fever in humans and reproductive failures in ruminants and camels. Arthropod detections in ticks and hedgehogs occur, but the main transmission routes involve birth products, milk, and dust aerosols rather than classical tick bites.

Moving Toward an Integrated One Health Framework

To bridge the gap between fragmented data sources, the review outlines a stepwise One Health surveillance workflow. This framework moves systematically from signal detection in human clinics, veterinary checks, or arthropod screens to targeted sampling, robust molecular confirmation, and evidence-based risk classification. By connecting clinical medicine, veterinary practice, entomology, and wildlife ecology, Tunisian researchers and public health authorities can better distinguish between high-priority zoonotic risks and harmless environmental microbes, ultimately strengthening national disease preparedness.

The research was published in Frontiers in microbiology on October 27, 2026.