American canine hepatozoonosis

Area of Science:

• Veterinary Parasitology
• Infectious Diseases
• Apical Complexa Biology

Background:

• American canine hepatozoonosis is an emerging tick-borne disease affecting domestic dogs.
• The causative agent is Hepatozoon americanum, a recently identified apicomplexan parasite.
• The Gulf Coast tick (Amblyomma maculatum) is the definitive host, while dogs and coyotes are intermediate hosts.

Purpose of the Study:

• To elucidate the transmission, pathogenesis, and life cycle of Hepatozoon americanum in dogs and ticks.
• To characterize the clinical and histopathological features of experimental canine hepatozoonosis.
• To investigate the susceptibility of coyotes to H. americanum infection.

Main Methods:

• Experimental infection of dogs and coyotes with H. americanum via oral administration of oocysts or infected ticks.
• Monitoring of clinical signs, hematological parameters, and histopathological changes.
• Investigation of parasite development stages in both intermediate hosts and the definitive tick host.

Main Results:

• Experimental canine disease developed 4-6 weeks post-exposure, characterized by systemic illness, neutrophilia, myositis, and periosteal bone proliferation.
• Histopathology revealed multifocal skeletal and cardiac myositis, rapid periosteal activation, osteogenesis, and occasional glomerulopathy/amyloidosis.
• Gamonts infectious to ticks appeared in canine peripheral blood leukocytes as early as 28 days post-exposure; coyotes developed indistinguishable disease.

Conclusions:

• Hepatozoon americanum can be experimentally transmitted to dogs and coyotes, causing significant clinical disease and pathological changes.
• The life cycle involves the Gulf Coast tick as the definitive host and canids as intermediate hosts.
• Understanding the parasite's biology and transmission is crucial for managing this emerging canine infection.