Moxidectin: heartworm disease prevention in dogs in the face of emerging macrocyclic lactone resistance.

Heartworm (Dirofilaria immitis) disease continues to increase and spread, remaining one of the most important and pathogenic parasitic diseases of dogs, despite the regular use of macrocyclic lactones (MLs) in preventive products. Dogs harboring strains of D. immitis resistant to MLs, the only drug class available for heartworm prevention in the United States, have been documented and proven.

Detection and cross-reaction of Dirofilaria repens using a commercial heartworm antigen test kit.

Antigen enzyme-linked immunosorbent assay tests are widely used for the diagnosis of heartworm infection in dogs. While commercially-available heartworm antigen tests have high sensitivity and specificity, false-negative test results can occur in dogs with low worm burdens, female-only infections, or prior to patency. The use of immune complex dissociation (ICD) methods have demonstrated increased sensitivity in the detection of Dirofilaria immitis antigens and the reversal of false-negative antigen results.

Clinical assessment of heartworm-infected Beagles treated with a combination of imidacloprid/moxidectin and doxycycline, or untreated.

Background: Administration of moxidectin topically and doxycycline PO has been utilized experimentally as an alternative treatment for heartworm disease. However, clinical effects of this protocol remain poorly characterized.

Objective: To evaluate the clinical and postmortem findings associated with administration of doxycycline and monthly 10% imidacloprid + 2.

Assessing the potential cross-reactivity using a commercial heartworm ELISA kits of serum from dogs naturally infected with Onchocerca lupi.

Onchocerca lupi is an emerging zoonotic parasite of dogs, endemic to the southwestern USA and areas of the Old World. Currently, there are no specific serological diagnostic tests able to detect O. lupi infection.

Canine gastrointestinal nematode transmission potential in municipal dog parks in the southeast United States.

Monthly canine parasite prophylactic products prevent not only adult heartworm infection, but also patent infections with specific gastrointestinal parasites. While most monthly products control and treat certain hookworm and roundworm infections, fewer are labeled for whipworm (Trichuris vulpis). Therefore, we hypothesized that fecal samples collected from municipal dog parks will have a greater prevalence of whipworm eggs compared to hookworm and roundworm eggs.

Acetic acid as an alternative reagent in the modified Knott test.

The suitability of acetic acid as a safer alternative to formalin in the modified Knott test was evaluated for the diagnosis of canine heartworm (Dirofilaria immitis). Microfilaria concentration was measured by both methods and found to agree within reasonable limits (-5.84 % bias; -88.

Efficacy and side effects of doxycycline versus minocycline in the three-dose melarsomine canine adulticidal heartworm treatment protocol.

Background: The American Heartworm Society currently recommends the use of a monthly macrocyclic lactone, a 28-day course of 10 mg/kg doxycycline BID, and the 3-dose protocol of melarsomine dihydrochloride for the treatment of canine heartworm disease. Doxycycline is necessary for the reduction of the bacterium Wolbachia, found in all heartworm life-stages. Previous price increases and decreasing availability prompted us to evaluate alternative tetracycline antibiotics, i.

Evaluation of heat-treating heartworm-positive canine serum samples during treatment with Advantage Multi for Dogs and doxycycline.

Background: The use of heat-treatment in canine and feline serum has been hypothesized to break the formation of antigen-antibody complexes, thereby freeing the heartworm antigen allowing for detection by commercially available heartworm antigen kits. While studies have analyzed the effect of heat-treating serum and plasma samples in the detection of heartworm antigen, these studies have not utilized necropsy verified results for validation. This study evaluated the use of heat-treating serum samples in experimentally infected dogs during adulticidal treatment in comparison with necropsy adult heartworm recovery.

Does evaluation of in vitro microfilarial motility reflect the resistance status of Dirofilaria immitis isolates to macrocyclic lactones?

Background: Several reports have confirmed that macrocyclic lactone-resistant isolates of Dirofilaria immitis are circulating in the United States; however, the prevalence and potential impact of drug resistance is unknown. We wished to assess computer-aided measurements of motility as a method for rapidly assessing the resistance status of parasite isolates.

Methods: Blood containing microfilariae (MF) from two clinical cases with a high suspicion of resistance was fed to mosquitoes and the resultant L3 injected into dogs that were then treated with six doses of Heartgard® Plus (ivermectin + pyrantel; Merial Limited) at 30-day intervals.

Assessment of parasitological findings in heartworm-infected beagles treated with Advantage Multi® for dogs (10% imidacloprid + 2.5% moxidectin) and doxycycline.

Background: Anecdotal reports support the position that the adulticidal heartworm treatment utilizing doxycycline and Advantage Multi®/Advocate® for Dogs (10% imidacloprid + 2.5% moxidectin) has successfully converted antigen-positive dogs to antigen-negative. To date, no controlled experimental studies have demonstrated the adulticidal efficacy of this treatment regimen.

Assessment of Blood Collection from the Lateral Saphenous Vein for Microfilaria Counts in Mongolian Gerbils (Meriones unguiculatus) Infected with Brugia pahangi.

The NIH guidelines for survival bleeding of mice and rats note that using the retroorbital plexus has a greater potential for complications than do other methods of blood collection and that this procedure should be performed on anesthetized animals. Lateral saphenous vein puncture has a low potential for complications and can be performed without anesthesia. Mongolian gerbils (Meriones unguiculatus) are the preferred rodent model for filarial parasite research.