David L. Huxsoll

Laboratory studies of tropical canine pancytopenia

Abstract Tropical canine pancytopenia (TCP) is a fatal, infectious disease of dogs characterized by hemorrhage, pancytopenia, and severe emaciation. The disease, which has been reported most frequently in the German Shepherd, has been responsible for the death of numerous military dogs in Southeast Asia. TCP has also occurred in Puerto Rico, the Virgin Islands, Florida, and the Mideast. The most striking clinical sign is a sudden onset of epistaxis in an apparently healthy dog. Pathological findings consist of petechial and ecchymotic hemorrhages on serosal and mucosal surfaces of numerous organs. The disease has been successfully transmitted to laboratory dogs. Experimentally infected beagles and mongrels develop clinical signs consistent with the natural disease; however, clinical signs of hemorrhage, including epistaxis, have been experimentally induced only in the German shepherd. Ehrlichia canis has been identified as the etiologic agent of TCP.

Tropical canine pancytopenia: Role of aplastic anaemia in the pathogenesis of severe disease

Abstract Previous studies of tropical canine pancytopenia (TCP), a disease of dogs caused by the rickettsia-like agent Ehrlichia canis , have suggested that dogs developing severe pancytopenia may have aplastic anaemia. In an attempt to elucidate the bone marrow lesion in dogs with severe TCP, we examined postmortem marrow sections as well as serial marrow aspirates from infected dogs. The histological marrow lesion in dogs with severe pancytopenia consisted of marked hypoplasia, depletion of megakaryocytes and ofter loss of normal sinusoidal architecture. Dogs chronically infected, but without severe pancytopenia, had normocellular marrows. Serial marrow aspirates revealed that the transient pancytopenia of the acute phase TCP is probably not related to total marrow failure, but that at 6 to 10 weeks after infection dogs that develop severe disease show marked depletion of megakaryocytes and early granulocytic precursors. The possibility of damage to marrow stroma or stem cells, perhaps with an immunopathological basis, is discussed.

Babesia microti: Pathogenesis of parasite of human origin in the hamster

Abstract The pathogenesis of the disease in hamsters caused by the first human Babesia isolant, tentatively named Babesia microti , and the immunologic relationship of the organism to Babesia canis were studied. The patent phase of the disease was characterized by severe anemia and marked parasitemia which occurred between the 6th and 41st day following infection. An increase in total white cell count with a neutrophilia, eosinophilia, monocytosis, and lymphocytosis was observed during the patent phase. The patent phase was followed by development of a carrier state. This was demonstrated by relapse following splenectomy 113 days after infection. No statistically significant differences were observed between the serum profiles of infected and noninfected animals during the period monitored. A serologic relationship between B. microti and B. canis was revealed by the use of gel diffusion and indirect fluorescent antibody (IFA) tests. The IFA test was used to monitor serum antibody responses during the patent and carrier phases of the disease. Crossabsorption studies between B. canis and B. microti revealed that the two organisms possess common and specific antigens.

Epizootiology of tropical canine pancytopenia.

Tropical canine pancytopenia (TCP) is a newly recognized infectious disease of dogs in diverse tropical and subtropical areas. The disease is characterized by hemorrhage, pancytopenia, severe emaciation and persistent infection. Dogs with TCP are often presented with epistaxis, which is the most dramatic sign of the disease; however, a large number of fnected dogs develop severe pancytopenia and die without manifesting clinical signs of hemorrhage. The disease has been reported most frequently in the German Shepherd. Pathological findings consist of petechial and ecchymotic hemorrhages on serosal and mucosal surfaces of numerous organs. The most prominent histological finding is a perivascular plasma cell infiltrate in most organs. Disease, indistinguishable from the natural disease, has been produced in laboratory dogs inoculated with whole blood from fnected dogs. Ehrlichia canis has been consistently recovered from all experimentally infected dogs. Attempts to transmit the disease to other laboratory animals and to propagate the agent in cell cultures and embryonating eggs have been unsuccessful. The tick is the probable vector of the disease.

RED AND GRAY FOXES — POTENTIAL RESERVOIR HOSTS FOR Ehrlichia canis1

Infection with Ehrlichia canis was successfully established in the red fox, Vulpes fulva, and the gray fox, Urocyon cinereoargenteus. Transtadial transmission of Ehrlichia canis from an infected fox to a laboratory Beagle dog by the tick, Rhipicephalus sanguineus, was demonstrated.

Recovery and characterization of a herpes-like virus from dog kidney cell cultures.

Summary A transmissible agent was recovered from primary DKTC which developed a spontaneous CPE. Characterization and serological studies of the virus indicated that the virus was a new member of the herpes virus group.

Babesia canis and Babesia gibsoni: Soluble and corpuscular antigens isolated from blood of dogs☆

Abstract Babesia canis and Babesia gibsoni were found to be serologically related on the basis of cross-reactions between corpuscular and soluble antigens derived from these organisms and sera of dogs recovered from acute infections caused by each of the parasites. By means of a gel-precipitation (GP) test each Babesia organism possessed at least one species-specific antigen. This antigenic difference was also indicated by the indirect hemagglutination (IHA) test. In the capillary-tube agglutination (CA) and indirect fluorescent antibody (IFA) tests, which used corpuscular antigens of these organisms and undiluted sera, serologic differences between the two organisms was not detected. The time of appearance of antibody detectable in the IHA test was closely correlated with the onset of the disease and appearance of the parasites in the peripheral blood. Based upon results obtained with sera of artificially and naturally infected dogs, the IHA test appears useful for detection and titration of antibodies in canine babesial infections.

Isolation and Characterization of a Neurotropic Agent (MHG Virus) from Adult Rats.

Summary A transmissible agent (MHG) with biological and physical properties similar to the viruses of the enterovirus group has been isolated from pooled tissues of 3 white rats, Sprague-Dawley strain, obtained from the Walter Reed Army Institute of Research animal colony. The agent produced fatal infections in both suckling rats and suckling mice when inoculated intracranially. A high incidence of complement-fixing antibodies against the new virus was found in adult human sera. The relationship of this virus to disease in man or animal has not been ascertained.