Comparison of the results of intradermal test reactivity and serum allergen-specific IgE measurement for Malassezia pachydermatis in atopic dogs.

BACKGROUND: Malassezia pachydermatis is part of the normal flora of canine skin. Malassezia hypersensitivity is recognized as a trigger for clinical signs of atopic dermatitis (AD) in some dogs. Determinations of Malassezia hypersensitivity are often made with intradermal testing (IDT), which may have limited availability in a first-opinion veterinary practice. HYPOTHESIS/OBJECTIVES: The purpose of this study was to compare immediate IDT reactivity to M. pachydermatis with results of an enzyme-linked immunosorbent assay (ELISA) designed to detect anti-Malassezia IgE. ANIMALS: Eighty-four dogs with a clinical diagnosis of AD. METHODS: Multi-allergen IDT was performed on all dogs. Serum testing for allergen-specific IgE against a panel of common environmental allergens and M. pachydermatis was performed by ELISA using the FcεRIα receptor fragment as a detection reagent, with results reported as adjusted optical density (OD). A receiver operating characteristic (ROC) curve was used to analyse the results of the two tests. RESULTS: The median adjusted OD of the anti-Malassezia IgE ELISA for dogs reactive and nonreactive to M. pachydermatis on IDT was 0.137 and 0.024, respectively. Analysis of the ROC curve suggested a cut-off point for the anti-Malassezia ELISA that yielded a sensitivity of 77.0% and a specificity of 89% relative to IDT results. CONCLUSIONS AND CLINICAL IMPORTANCE: Substantial agreement was demonstrated between IDT reactivity and anti-Malassezia IgE as detected by the FcεRIα receptor reagent. Although correlation with a clinical diagnosis of Malassezia dermatitis was not attempted in this study, the results indicate that the ELISA may be used to demonstrate the presence of immediate-type Malassezia hypersensitivity in dogs with AD.

Transplacental transmission of a North American isolate of Leishmania infantum in an experimentally infected beagle.

Leishmania infantum, an etiologic agent of zoonotic visceral leishmaniasis, is widespread among foxhounds in the United States. Although sand flies are widely distributed throughout the United States, epidemiological data do not support a major role for sand flies in the transmission of L. infantum in foxhounds in this country. Congenital transmission of human visceral leishmaniasis is reported in humans and might also occur in dogs. We have previously isolated L. infantum from Virginia foxhounds and used this isolate (LIVT-1) to experimentally infect beagles. Four female beagles, chronically infected with LIVT-1, were bred to a male beagle chronically infected with L. infantum chagasi. One beagle was able to maintain her pregnancy, and 4 puppies were delivered by cesarean section. One puppy was malformed and autolytic at delivery, and tissues were not collected or analyzed. The remaining puppies were killed at the time of cesarean section, and selected tissues were collected for parasite culture and PCR. Promastigotes were not cultured from tissues in any of the puppies. Leishmania sp. DNA was detectable by PCR in liver, bone marrow, and heart from all 3 puppies and in the spleen, lymph node, kidney, and placenta in 2 puppies. Placental tissue from the dam was PCR negative. This is the first report of maternal transmission of a North American isolate of L. infantum from an experimentally infected dog.

Selection of HPRT primers as controls for determination of mRNA expression in dogs by RT-PCR.

Reliable housekeeping gene controls are critical for measuring and comparing gene expression at the transcription level by Northern blot and RT-PCR. In order to develop such controls for studying cytokine mRNA expression in dogs, DNA sequence encoding a full-length canine HPRT protein has been obtained. Numerous primer pairs derived from the canine HPRT sequence have been tested on canine genomic DNA as well as cDNA. The data from the present study suggest that there may be processed HPRT pseudogenes in dogs. Three pairs of canine HPRT primers designed and tested in the present study were able to differentiate between cDNA and genomic DNA under specific PCR conditions. These primers would be useful controls for measurement of mRNA expression by RT-PCR in the dog.