Evaluation of the speed of kill of fleas and ticks with Frontline Top Spot in dogs.

The speed of kill of a spot-on formulation of fipronil (Frontline Top Spot, Merial Limited, Duluth, GA) against adult cat fleas (Ctenocephalides felis) and brown dog ticks (Rhipicephalus sanguineus) was evaluated in dogs in a commercial laboratory setting. Forty dogs were allocated to 20 replicates of two based on sex and pretreatment flea counts. Within each replicate, dogs were randomly allocated to an untreated control group or to treatment with fipronil, administered topically as a spot-on per label instructions. The technical staff performing the flea and tick counts were unaware of treatment group assignments. Each dog was infested with approximately 100 unfed adult fleas on Day -8 or -6 and on Day -1. Each dog also was infested with approximately 50 unfed adult ticks on Day -1. Treatments were administered on Day 0 according to body weight. Flea and tick counts were performed on four randomly selected dogs from each treatment group at approximately 6, 12, 18, 24, and 48 hours after treatment. Flea and tick count reductions for dogs treated with fipronil were significant (P < .05), as compared with untreated controls, at 18, 24, and 48 hours after treatment. Controlled efficacy of fipronil against C. felis and R. sanguineus ranged from 94% to 100% at these evaluation times. This study demonstrated that the speed of kill of fipronil, applied topically as a spot-on, was 100% against C. felis fleas on dogs within 12 to 18 hours after treatment and 100% against R. sanguineus ticks between 24 and 48 hours after treatment.

Prevalence of feline heartworm infections among cats with respiratory and gastrointestinal signs: results of a multicenter study.

Although heartworm infection in cats was first described in 1921, the diagnosis of the infection remains elusive in many cases. This is due to nonspecific clinical signs of feline heartworm disease, typically low worm burdens, unique pathophysiology in the cat, and the limitations of currently available heartworm tests. Consequently, knowledge about this disease is still limited. An objective of this study was to survey the occurrence and clinical presentation of feline heartworm infection among cats presenting with clinical signs consistent with heartworm disease. Two-hundred fifteen cases were submitted from 15 private practices in Florida, South Carolina, Tennessee, and Texas. Cats entered in the study were at least 6 months of age and presented with one or more of the following clinical signs: respiratory signs, including tachypnea, dyspnea, or coughing; gastrointestinal signs, including a pattern of intermittent vomiting unrelated to eating; or sudden death of uncertain etiology, particularly associated with respiratory distress prior to death. Data collected included: history and indoor/ outdoor lifestyle; physical examination findings; thoracic radiography evaluations; Knott or DIFIL test results, DiroCHEK antigen test results, and antibody test results (Animal Diagnostics, Inc. and Heska Corporation); and CBC results. Recheck examinations were scheduled for any cat with positive heartworm serological test results and for cats with radiographic signs consistent with or suggestive of feline heartworm disease. Data from 215 cases were collected and analyzed: 94/215 (44%) tested antibody positive for one or both antibody tests that were performed; 18/94 (19%) of the antibody-positive cats were reported as living 100% indoors by their owners; (12%) of the antibody-positive cats spent less than or equal to 10% of their time outdoors. Eleven of 215 cats (5%) were DiroCHEK antigen positive on initial examination. One cat was both DiroCHEK and microfilariae positive, but negative for both antibody tests. Radiographs were obtained for 10 of these cats and 6/10 had radiographic signs consistent with or suggestive of feline heartworm infection. At necropsy, heartworms were found in one other cat from which blood was not obtained. Additionally, two cats that had positive radiographic signs of heartworm infection converted from antigen-negative to antigen-positive status at recheck examination for a total of 13/215 (6%) DiroCHEK antigen-positive cats. One case that was submitted after acute death was DiroCHEK antigen positive, but interestingly, had relatively low antibody levels for both antibody tests. Initial radiographs were available on 212 of the 215 cases. In 90/212 (42%) cases, initial thoracic radiographs showed signs consistent with or suggestive of heartworm disease. Follow-up radiographs showed varying progression with radiographic signs worsening, improving, or staying the same on individual cats. Feline heartworm disease should be among the primary differential diagnoses in cats with respiratory disease, vomiting, or acute death. Radiography, antibody testing, and antigen testing are all useful tools to aid in making the diagnosis. A confirmed diagnosis may require doing multiple tests and clinical reevaluation. Cats classified by their owners as indoor only cats were found to be heartworm infected, thus lifestyle of the cat cannot rule out the disease. Actual antibody levels (high or low) may not correspond to severity of disease.

Radiographic diagnosis of feline heartworm disease and correlation to other clinical criteria: results of a multicenter clinical case study.

Two-hundred fifteen cats with clinical signs consistent with feline heartworm disease (FHD) were entered into this clinical case study. In addition to physical examination, CBC, and heartworm antibody (Ab) and antigen (Ag) tests, thoracic radiographs were taken of 212 cats at initial examination. For cats that had a positive Ab or Ag test, or radiographic changes that could be associated with FHD, follow-up radiographs were taken at approximately 60 to 90 days after initial examination whenever possible. Each radiographic examination included VD, DV, and left lateral views, and each was read by the same board-certified radiologist who was blinded to heartworm serological results until after radiographic evaluation was completed. Criteria evaluated included heart size and shape, pulmonary artery enlargement, pulmonary parenchymal involvement, hyperinflation of lungs, tenting of the diaphragm, and pleural fluid accumulation. Summary interpretations and heartworm score were recorded. The heartworm score reflected the degree of suspicion of FHD based on radiographic signs: no radiographic signs of FHD; bronchointerstitial lung pattern only (consistent with but not specific for FHD); or pulmonary artery enlargement (with or without pulmonary or cardiac changes) mildly, moderately, or strongly indicative of FHD. Of 212 cats for which radiographs were taken at the initial examination, 38 (18%) had enlarged caudal lobar arteries indicative of FHD and 90 (42%) had bronchointerstitial pulmonary disease consistent with heartworms and/or enlarged caudal lobar arteries. Radiographic changes consistent with or indicative of FHD were evident in 9/22 cats (41%) presenting with gastrointestinal signs, 39/78 cats (50%) presenting with respiratory signs, and 41/80 cats (51%) presenting with both respiratory and gastrointestinal signs. Some cats presenting with only gastrointestinal signs had thoracic radiographic changes suggestive of FHD. Eleven cats tested DiroCHEK Ag positive, and radiographs were taken of 10. Of the 10 cats, 5 had radiographic changes indicative of FHD; one had changes consistent with FHD; and 4 cats showed no radiographic signs of FHD. Follow-up radiographs were taken of 6 of these 11 cats: 1/6 worsened in radiographic score, 3/6 improved in radiographic score, and 2/6 still demonstrated no radiographic signs of heartworm. Ninety-two cats tested Ab positive at initial examination, and radiographs were available for 91 of these cats. In 22/91 (24%), enlarged caudal lobar arteries indicated FHD. In 39/91 cats (43%) cats, radiographic signs consistent with or indicative of FHD were seen. Of the 38 cats that had radiographic signs indicative of FHD, 22 (58%) were Ab positive on one or both tests. Seven (32%) had positive DiroCHEK Ag tests at initial or recheck examination. At recheck examinations, 2 cats that initially had radiographic signs indicative of FHD converted from DiroCHEK Ag negative to positive, confirming their infection with at least 1 sexually mature female heartworm. While many affected cats show pulmonary arterial enlargement and/or a bronchointerstitial pattern typical of FHD, some cats with serologic evidence of heartworms do not demonstrate any thoracic radiographic changes. Conversely, some cats show radiographic signs suggesting heartworm disease when concurrent serology is negative. These discrepancies may be caused by time between infection and examination, by differences in individual cats' immune response to the presence of larval or adult stages of heartworm, or by aberrant migrations.

Feline heartworm disease: correlations of clinical signs, serology, and other diagnostics--results of a multicenter study.

In cooperation with 15 practices in Florida, South Carolina, Tennessee, and Texas, data were collected on 215 cats with signs consistent with feline heartworm disease (FHD). Cats included in the study were over 6 months of age and presented with primary complaints of coughing or dyspnea, vomiting unrelated to eating, or acute death. Detailed signalment, thoracic radiographs, CBC, Knott or DIFIL test, DiroCHEK antigen test (Ag), and antibody (Ab) tests performed by Animal Diagnostics (AD) and Heska Corp (HC) were collected on each cat. Any cat that had positive antibody or antigen tests, and any cat with radiographic signs suggestive of FHD was scheduled for recheck examinations at 30 to 45 days and/or 60 to 90 days after initial presentation. This study was designed to identify cats with concurrent or previous FHD, and to better characterize the presentation of this disease by following their progress. Of the 215 cats, 94 (44%) were Ab positive based on one or both tests. This indicated that the cat had been successfully infected with third-stage heartworm larvae and those larvae had developed to at least the fourth stage. Of the Ab-positive cats, 23/94 (24%) presented with vomiting; 39/94 (41%) presented with respiratory signs; and 27/94 (29%) had vomiting and respiratory signs. Discordant results between the AD and HC antibody tests occurred, with the AD test detecting a higher number of antibody-positive cats. When comparing results of these Ab tests, no correlation was seen between the intensity of Ab level measured by the two tests, suggesting that different Ab is detected. One cat that died acutely with signs associated with FHD had relatively low Ab detected on both tests but had a positive DiroCHEK antigen test. No correlation between the level of antibody and the severity of clinical signs or radiographic pattern was found. Eleven cars were DiroCHEK Ag positive on initial presentation. Of the Ag-positive cats, 2 were AD negative and 3 were HC negative. One cat was Ag positive and microfilaria positive but negative for Ab with both AD and HC tests. Although it has been presumed that most cats with FHD are Ag negative, it would appear that some individual cats with adult heartworms can also be Ab negative. Although eosinophilia and basophilia were more frequently associated with cats that were Ab positive, abnormal CBC values were observed in cats that were currently Ab negative. Radiographic lesions did not correlate with clinical signs or Ab levels. Some cats with no radiographic signs of FHD were Ag positive. Further, some cats with typical radiographic lesions of FHD were negative based on all serologic evaluations. These results demonstrate that successful transmission of heartworms to cats is more common than previously thought and is clinically associated with coughing, dyspnea, and vomiting. A cause and effect correlation cannot be proven between clinical signs and laboratory evaluation. Radiographic evidence of FHD in cats with repeated negative antibody results may be an indicator of residual damage from previous heartworm infections. Most experimental studies of FHD have been short-term (< 1 yr). However, in this study, many cats underwent repeated clinical evaluation over a relatively short time. This demonstrated that the clinical picture of spontaneous FHD is a constantly changing syndrome, highly dependent on the stage (immature L5, adult, adult death, residual damage) of the parasite in the cat and the individual cat's response. On evaluation of clinically affected cats, no one test proved to be definitive (without exceptions). The diagnosis of FHD continues to require a combination of clinical evaluation and a series of diagnostic tests, often requiring reevaluations over time.