Interaction between canine platelets and adult heartworms: platelet recognition of heartworm surfaces.

An interaction between blood platelets and adult heartworms was examined in vitro. Surfaces of glutaraldehyde-fixed heartworms, which were taken from infected dogs washed, and incubated in platelet-rich plasma (PRP), were evaluated by scanning electron microscopy. Adherence of platelets to heartworms occurred only with PRP from infected dogs. Aggregation to epinephrine and adenosine diphosphate of PRP incubated with heartworms was monitored. Seemingly, platelet activation to heartworm membranes occurs in dogs with heartworm disease. The increased platelet reactivity was also observed in dogs with occult heartworm disease, indicating that the presence of circulating microfilaria was not important for this process. The ability to transfer the reactivity to heartworm-negative platelets by suspending them in heartworm-positive plasma indicated that this reactivity resided in the plasma. The processes leading to platelet activation may be responsible for the platelet-associated vascular disorders of canine heartworm disease.