Epidemiological, clinical, and laboratory characteristics of human granulocytic anaplasmosis in North India

Abstract

Human granulocytic anaplasmosis (HGA) is an emerging, rickettsial tick-borne disease caused by Anaplasma phagocytophilum. Sero-epidemiological data demonstrate that this pathogen has a worldwide distribution. The diagnosis of HGA requires a high index of clinical suspicion, even in endemic areas. In recent years, HGA has increasingly been reported from Asia and described in China, Japan, and Korea. We serologically and molecularly screened 467 patients with clinical suspicion of Anaplasmosis. The present study describes the epidemiology, clinical, and laboratory details of 6 confirmed and 43 probable cases of human granulocytic anaplasmosis. One of the HGA patients developed secondary invasive opportunistic Aspergillus fumigatus and Acinetobacter baumanii infection during the illness, which resulted in a fatal infection. The HGA patients without severe complications had excellent treatment responses to doxycycline. The emergence of this newly recognized tick-borne zoonotic HGA in North India is a significant concern for public health and is likely underdiagnosed, underreported, and untreated. Hence, it is also essential to establish a well-coordinated system for actively conducting tick surveillance, especially in the forested areas of the country.IMPORTANCEThe results of the present study show the clinical and laboratory evidence of autochthonous cases of Anaplasma phagocytophilum in North India. The results suggest the possibility of underdiagnosis of HGA in this geographical area. One of the HGA patients developed secondary invasive opportunistic Aspergillus fumigatus and Acinetobacter baumanii infection during the illness, which resulted in a fatal infection.

Keywords: Anaplasma phagocytophilum; human granulocytic anaplasmosis; immunoblot; leukopenia; thrombocytopenia; tick-borne disease.

Fig 1

Real-time PCR linear amplification plot of A. phagocytophilum six positive samples

Fig 2

A. phagocytophilum-specific IgG immunoblot results of three representative samples. (a) Positive for p44, Asp62, and borderline for OmpA antigens; (b) positive for Asp62 and OmpA antigens; (c) negative sample.

Fig 3

The geographical location of HGA-positive cases. (The figure was created using MapChart.)