BackgroundLong‐term microscopic agglutination test (MAT) results after vaccination with 4‐serovar Leptospira vaccines are not available for all vaccines used in client‐owned dogs.Hypothesis/ObjectivesTo determine antibody responses of client‐owned dogs given 1 of 4 commercially available Leptospira vaccines.AnimalsHealthy client‐owned dogs (n = 32) with no history of Leptospira vaccination for at least the previous year.MethodsDogs were given 1 of 4 Leptospira vaccines on week 0 and then approximately on week 3 and week 52. Sera were collected before vaccine administration on week 0 and then within 3 days of week 3, within 2 days of week 4, and approximately on weeks 7, 15, 29, 52, and 56. Antibody titers against Leptospira serovars bratislava, canicola, grippotyphosa, hardjo, icterohemorrhagiae, and pomona and were determined by MAT.ResultsWhen compared among vaccines, MAT results varied in maximal titers, the serovars inducing maximal titers, and the time required to reach maximal titers. Each vaccine induced at least some MAT titers ≥1 : 800. Most dogs were negative for antibodies against all serovars 1 year after vaccination, and anamnestic responses were variable.Conclusions and Clinical ImportanceDogs vaccinated with Leptospira vaccines have variable MAT titers over time, and antibodies should not be used to predict resistance to Leptospira infection. MAT titers ≥1 : 800 can develop after Leptospira spp. vaccination, which can complicate the clinical diagnosis of leptospirosis.

Healthcare personnel (HCP) are at potential risk for SARS-CoV-2 infection in occupational and non-occupational settings, even when fully vaccinated. This risk has increased during Delta variant circulation. SARS-CoV-2 testing of fully vaccinated HCP working in the 14 days after exposure is important to prevent virus introduction into healthcare settings.

Heartworm disease in cats has been attributed to immature adult heartworms reaching the pulmonary arteries approximately 2.5 -4 months post infection and the presence of mature adult worms in the cardiopulmonary system approximately 6 months after infection. The arrival and death of immature heartworms causes significant lung pathology, a condition referred to as heartwormassociated respiratory disease (HARD). To evaluate the humoral immune response to Dirofilaria immitis, 12 cats were each infected by subcutaneous injection of 100 third-stage larvae. Postinfection serum samples were collected weekly for 4 weeks, every other week for the following 4 weeks, then monthly to day 270 for evaluation of antibodies to D. immitis recombinant antigens HWAg-1 and HWAg-2 and circulating heartworm antigen (HWAg) using the PetChek ® HTWM PF Test Kit (IDEXX Laboratories). Necropsies were performed 278 -299 days post infection for collection of adult worms. Eleven cats were HWAg-1 antibody-positive 68 days post-infection, and the remaining cat became positive by day 140. Eleven cats were positive for HWAg-2 antibody 42 -84 days post infection; all 11 remained HWAg-2 antibodypositive through day 270. Circulating HWAg was detected in 10 cats, 2 by day 140 and 8 others by day 168. The 2 antigen-negative cats had no adult worms at necropsy. This study demonstrates that decomposition of immature adult heartworms can result in detectible levels of circulating antigen prior to sexual maturation. In this experimental Original Article S92EndoparasitEs model, D. immitis antigen was detectable in cats at time points (days 140 and 168) associated with HARD from dying immature adult heartworms.