Serological Evidence of Anaplasma phagocytophilum and Spotted Fever Group Rickettsia spp. Exposure in Horses from Central Italy.

Valentina Virginia Ebani

doi:10.3390/pathogens8030088

Abstract

Anaplasma phagocytophilum and Rickettsia spp. are tick-borne bacteria of veterinary and human concern. In view of the One-Health concept, the present study wanted to evaluate the spreading of these pathogens in horses living in central Italy. In particular, the aim of the investigation was to verify the exposure to A. phagocytophilum in order to update the prevalence of this pathogen in the equine population from this area, and to spotted fever group (SFG) Rickettsia spp. to evaluate a possible role of horses in the epidemiology of rickettsiosis. Indirect immunofluorescent assay was carried out to detect antibodies against A. phagocytophilum and SFG (spotted fever group) Rickettsia spp. in blood serum samples collected from 479 grazing horses living in central Italy during the period from 2013 to 2018. One hundred and nine (22.75%) horses were positive for A. phagocytophilum, 72 (15.03%) for SFG Rickettsia spp., and 19 (3.96%) for both antigens. The obtained results confirm the occurrence of A. phagocytophilum in equine populations, and also suggest the involvement of horses in the epidemiology of SFG rickettsiosis. In both cases, in view of the zoonotic aspect of these pathogens and the frequent contact between horses and humans, the monitoring of equine populations could be useful for indication about the spreading of the tick-borne pathogens in a certain geographic area.

Highlights

Hematophagous arthropods, especially ticks, are well-known as vectors of several bacterial, viral, and protozoan pathogens
One hundred and nine (22.75%) horses were positive for A. phagocytophilum, (15.03%) for spotted fever group (SFG) Rickettsia spp., and 19 (3.96%) for both antigens
Nineteen (3.96%) horses had antibodies to both A. phagocytophilum and SFG Rickettsia spp

Summary

Introduction

Hematophagous arthropods, especially ticks, are well-known as vectors of several bacterial, viral, and protozoan pathogens. Anaplasma phagocytophilum and Rickettsia spp. may induce clinical manifestations in humans and different animal species. Anaplasma phagocytophilum is an obligate intracellular, Gram negative bacterium belonging to the order Rickettsiales, family Anaplasmataceae. It is able to infect granulocytes, mainly neutrophils, of several domestic and wild animal species [1]. Wild mammals usually serve as asymptomatic reservoirs of A. phagocytophilum, whereas domestic animals may develop clinically defined diseases, such as tick-borne fever in cattle and sheep and granulocytic anaplasmosis in dogs [2]. A. phagocytophilum is cause of infection in human beings, who develop a disease called human granulocytic anaplasmosis (HGA), varying from mild to severe forms with fever, headache, myalgia, arthralgia, leukopenia, and thrombocytopenia; serious opportunistic infections can occur in immunocompromised patients during the course of HGA [3]

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