{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,5,30]],"date-time":"2026-05-30T08:01:38Z","timestamp":1780128098508,"version":"3.54.0"},"posted":{"date-parts":[[2026,5,27]]},"group-title":"Microbiology","reference-count":79,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T00:00:00Z","timestamp":1779840000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,5,27]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>\n                  Tick-borne pathogens can reshape vector microbiomes in ways that influence pathogen colonisation and transmission, yet the interplay between\n                  <jats:italic>Ehrlichia ruminantium<\/jats:italic>\n                  and the microbiota of its tick vectors remains uncharacterised. We profiled bacterial communities in haemolymph, midgut, and salivary glands of infected (n = 11) and uninfected (n = 12)\n                  <jats:italic>Am. gemma<\/jats:italic>\n                  ticks, a vector of\n                  <jats:italic>E. ruminantium<\/jats:italic>\n                  in East Africa, collected from cattle in Kajiado County, Kenya, using near-full-length 16S rRNA gene amplicon sequencing on the Oxford Nanopore platform. Community composition, alpha and beta diversity, co-occurrence networks, keystone taxa, and PICRUSt2-inferred functional profiles were compared across tissue\u2013infection status groups. We identified 226 bacterial genera dominated by\n                  <jats:italic>Coxiella<\/jats:italic>\n                  ,\n                  <jats:italic>Pseudomonas<\/jats:italic>\n                  ,\n                  <jats:italic>Acinetobacter<\/jats:italic>\n                  ,\n                  <jats:italic>Proteus<\/jats:italic>\n                  , and\n                  <jats:italic>Rickettsia<\/jats:italic>\n                  . Infection was associated with tissue-specific shifts in community composition (PERMANOVA\n                  <jats:italic>R<\/jats:italic>\n                  \u00b2 = 0.14,\n                  <jats:italic>p<\/jats:italic>\n                  &lt; 0.001) and co-occurrence network structure, with midgut networks showing complete hub taxon turnover (Jaccard = 0.000,\n                  <jats:italic>p<\/jats:italic>\n                  = 0.043). Haemolymph communities converged around\n                  <jats:italic>Luteimonas<\/jats:italic>\n                  as a keystone taxon, while opportunistic Proteobacteria, including\n                  <jats:italic>Acinetobacter<\/jats:italic>\n                  and\n                  <jats:italic>Serratia<\/jats:italic>\n                  , emerged as keystones in infected midgut. Endosymbiotic\n                  <jats:italic>Rickettsia<\/jats:italic>\n                  was near-absent in infected tissues (0.3% vs 9.3% mean relative abundance in midgut), consistent with competitive exclusion. Functional inference identified FDR-significant enrichment of predicted aerobactin siderophore biosynthesis, antimicrobial efflux, and oxidative stress response gene families in infected microbiota. These findings show tissue-specific restructuring of the\n                  <jats:italic>Am. gemma<\/jats:italic>\n                  microbiome associated with\n                  <jats:italic>E. ruminantium<\/jats:italic>\n                  infection and point to candidate targets for microbiome-based interventions against heartwater.\n                <\/jats:p>\n                <jats:sec>\n                  <jats:title>Importance<\/jats:title>\n                  <jats:p>\n                    Heartwater, caused by the bacterium\n                    <jats:italic>Ehrlichia ruminantium<\/jats:italic>\n                    and transmitted by\n                    <jats:italic>Amblyomma<\/jats:italic>\n                    ticks, kills up to 90% of susceptible ruminants and is one of the most devastating tick-borne diseases in sub-Saharan Africa. Controlling heartwater requires understanding how the pathogen interacts with the microbial communities living inside its tick vector. In this exploratory study, we show that\n                    <jats:italic>E. ruminantium<\/jats:italic>\n                    infection is associated with tissue-specific shifts in the\n                    <jats:italic>Amblyomma<\/jats:italic>\n                    tick microbiome, including reduced abundance of beneficial symbionts, elevated representation of opportunistic bacteria among community hubs, and enrichment of iron acquisition and antimicrobial resistance functions. The midgut, the first tissue colonised during infection, showed the most marked structural reorganisation. These tissue-resolved microbiome signatures point to potential targets for novel control strategies, such as anti-microbiota vaccines or approaches that reinforce natural colonisation resistance, offering new strategies to reduce heartwater transmission and protect livestock livelihoods across Africa.\n                  <\/jats:p>\n                <\/jats:sec>","DOI":"10.64898\/2026.05.26.727963","type":"posted-content","created":{"date-parts":[[2026,5,28]],"date-time":"2026-05-28T06:10:16Z","timestamp":1779948616000},"source":"Crossref","is-referenced-by-count":0,"title":["<i>Ehrlichia ruminantium<\/i>\n                  infection is associated with tissue-specific microbial community shifts in\n                  <i>Amblyomma gemma<\/i>\n                  ticks from cattle in Kenya"],"prefix":"10.64898","author":[{"given":"Dennis","family":"Getange","sequence":"first","affiliation":[{"name":"International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772-00100, Nairobi, Kenya"},{"name":"School of Agriculture and Science, Westville Campus, University of KwaZulu-Natal, Private Bag X54001, Durban, 4000, South Africa"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Samson","family":"Mukaratirwa","sequence":"additional","affiliation":[{"name":"School of Agriculture and Science, Westville Campus, University of KwaZulu-Natal, Private Bag X54001, Durban, 4000, South Africa"},{"name":"One Health Centre for Zoonoses and Tropical Veterinary Medicine, Ross University School of Veterinary Medicine, Basseterre, St Kitts and Nevis, West Indies"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dorcas","family":"Chebet","sequence":"additional","affiliation":[{"name":"International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772-00100, Nairobi, Kenya"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"James","family":"Kabii","sequence":"additional","affiliation":[{"name":"International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772-00100, Nairobi, Kenya"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rua","family":"Khogali","sequence":"additional","affiliation":[{"name":"International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772-00100, Nairobi, Kenya"},{"name":"Department of Parasitology, Faculty of Veterinary Medicine, University of Khartoum, P.O. Box 32, Khartoum North, Sudan"},{"name":"Department of Medicine and Animal Production, University of Naples Federico II, Naples, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jandouwe","family":"Villinger","sequence":"additional","affiliation":[{"name":"International Centre of Insect Physiology and Ecology (icipe), P.O. 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