Introduction

• Cause: tick-borne infection with Anaplasma spp. including A. phagocytophilum and A. platys.
• Signs: pyrexia, lethargy, anorexia and musculoskeletal pain in acute infections.
• Diagnosis: detection of morulae on blood smear, serology, PCR.
• Treatment: doxycycline.
• Prognosis: usually mild disease - no deaths due to sole infection with A. phagocytophilum or A. platys have yet been reported.
• Anaplasma phagocytophilum infects a wide range of mammals but clinical illness documented in cats, dogs, horses, cattle, sheep, goats, llamas, and humans.
• Reported sero- and molecular-prevalences are reported in humans, cats, dogs, horses, and other potential reservoir host species from the same area, suggesting that variant A. phagocytophilum strains may exist in different host species.

Pathogenesis

Etiology

• A. phagocytophilum.
• A. platys.

Predisposing factors

General

• Lack of adequate tick control Tick control.
• Exposure to tick habitat (eg indoor/outdoor or outdoor cat).

Specific

• Infected Ixodes spp ticks Ixodes ricinus with A. phagocytophilum.
• Suspected Rhipicephalus sanguineus ticks with A. platys (not confirmed to be the vector in experimental transmission studies).

Pathophysiology

• Co-infection with other vector-borne pathogens may lead to the development of clinical signs or the worsening of the severity of disease. Ixodes spp ticks also vector Borrelia burgdorferi, while R. sanguineus is the vector of many agents, of which Ehrlichia canis or an E. canis-like agent has been reported to infect cats.

Timecourse

• Based on information from experimental transmission studies to mice, attachment/feeding of Ixodes spp ticks for 24 hours resulted in infection with A. phagocytophilum, indicating that transmission occurred before the 24 hour mark.
• The transmission time from tick to animal for A. platys has not been determined in experimental transmission studies.
• Disease incubation after tick bite is 1–2 weeks.
• Cats may maintain infection for months, often without concurrent illness.

Epidemiology

• Anaplasma phagocytophilum is transmitted by bites from Ixodes spp tick vectors, especially:
  • Ixodes pacificus on the western coast of United States.
  • Ixodes scapularis in the north-eastern, upper Midwest/Great Lakes regions, and areas along the Atlantic seaboard (Virginia northward). This tick is also responsible for transmission in areas of Canada bordering the Great Lakes and from New York to Maine.
    • Both I. pacificus and I. scapularis are vectors for Borrelia burgdorferi in the U.S. and Canada.
  • Ixodes ricinus throughout Europe
    • I. ricinus is the vector for Borrelia burgdorferi and Tick-borne Encephalitis virus in Europe and western parts of Asia.
  • Ixodes persulcatus across sections of Russia and northern Asia.
• Wildlife, such as rodents and other small mammals, act as the reservoir hosts, with transmission to domestic animals and man as a result of tick attachment and feeding.
• Wild ruminants, such as deer, may also act as reservoirs for selected strains of Anaplasma spp.
• It has been suggested that the infection can be introduced into disease-free areas by migrating birds.

Diagnosis

Treatment

Prevention

Outcomes