Abstract
.Human granulocytic anaplasmosis (HGA), caused by the bacteria Anaplasma phagocytophilum, is transmitted to humans by blacklegged ticks (Ixodes scapularis) in eastern North America. To assess the emergence of A. phagocytophilum in Ontario, we analyzed patient serological and clinical data in combination with pathogen detection in blacklegged ticks from 2011 to 2017. Our sample population included all patients who had Anaplasma serological testing ordered by their physicians (n = 851). Eighty-three patients (10.8%) were A. phagocytophilum seropositive (IgG titers ≥ 1:64) and 686 (89.2%) were seronegative (IgG titers < 1:64). Applying published surveillance case definitions, we classified zero as confirmed, five as probable, and 78 as suspected cases. The percentage of seropositive patients remained generally stable at 13.6%. Seropositive patients were most often adult females, 40–59 years of age, and reported nonspecific signs and symptoms, such as fatigue, headache, and fever. Higher seropositivity rates (≥ 1.5 patients per 100,000 population) occurred in eastern and northwestern Ontario. The percentage of A. phagocytophilum-positive blacklegged ticks, through passive and active surveillance, was 0.4 and 1.1%, respectively, and increased over time. Serological and entomological indicators of A. phagocytophilum activity increased in areas of the province with established blacklegged tick populations. The risk of HGA is presently low in Ontario; however, further research is required to document the epidemiology of HGA in the province. To minimize the impact of HGA emergence in Ontario, increased awareness and education of the public and health-care providers is recommended, with consideration to making HGA a reportable infection in Ontario.
Highlights
Human granulocytic anaplasmosis (HGA) is a tick-borne disease caused by the obligate, intracellular bacteria Anaplasma phagocytophilum
Sera from 851 patients were tested for A. phagocytophilum antibodies from 2011 through 2017; 97 patients (11.4%) were seropositive (IgG titer 3 1:64) and 754 (88.6%) were seronegative (IgG titer < 1:64)
Applying the U.S CDC surveillance case definitions to 83 seropositive patients in Ontario, we classified zero as confirmed, five as probable, and 78 as suspected cases
Summary
Human granulocytic anaplasmosis (HGA) is a tick-borne disease caused by the obligate, intracellular bacteria Anaplasma phagocytophilum. Anaplasma phagocytophilum infects granulocytes (i.e., neutrophils) and early infection, while often asymptomatic, can present as a febrile illness with nonspecific symptoms, such as arthralgia, headache, malaise, and myalgia; less common symptoms include a stiff neck, gastrointestinal complaints, and cough.[1,2] Laboratory abnormalities in HGA patients include thrombocytopenia, leukopenia, elevated creatinine levels, anemia, and elevated hepatic transaminase levels.[2,3] Most patients recover fully after appropriate antibiotic treatment; if untreated, the infection can lead to serious outcomes, such as neurological complications, opportunistic secondary infections, disseminated intravascular coagulation, organ failure, and acute respiratory distress.[3,4] Severe illness is more common in patients older than 50 years and those with immunocompromising conditions (e.g., undergoing chemotherapy or organ transplant).[5,6] Deaths from A. phagocytophilum infections are rare and, in the United States, case fatality rates are £ 1%.4,5. Anaplasma phagocytophilum infects granulocytes (i.e., neutrophils) and early infection, while often asymptomatic, can present as a febrile illness with nonspecific symptoms, such as arthralgia, headache, malaise, and myalgia; less common symptoms include a stiff neck, gastrointestinal complaints, and cough.[1,2] Laboratory abnormalities in HGA patients include thrombocytopenia, leukopenia, elevated creatinine levels, anemia, and elevated hepatic transaminase levels.[2,3] Most patients recover fully after appropriate antibiotic treatment; if untreated, the infection can lead to serious outcomes, such as neurological complications, opportunistic secondary infections, disseminated intravascular coagulation, organ failure, and acute respiratory distress.[3,4] Severe illness is more common in patients older than 50 years and those with immunocompromising conditions (e.g., undergoing chemotherapy or organ transplant).[5,6] Deaths from A. phagocytophilum infections are rare and, in the United States, case fatality rates are £ 1%.4,5 Human granulocytic anaplasmosis occurs worldwide, with the highest incidence in North America
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: The American journal of tropical medicine and hygiene
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
