Author Archives: Grupo MVeIT

Macrocyclic lactone resistance in Dirofilaria immitis: Failure of heartworm preventives and investigation of genetic markers for resistance.

Vet Parasitol. 2015 Jun 15; 210(3-4):167-78.

doi: 10.1016/j.vetpar.2015.04.002. Epub 2015 Apr 13

Bourguinat C, Lee AC, Lizundia R, Blagburn BL, Liotta JL, Kraus MS, Keller K, Epe C, Letourneau L, Kleinman CL, Paterson T, Gomez EC, Montoya-Alonso JA, Smith H, Bhan A, Peregrine AS, Carmichael J, Drake J, Schenker R, Kaminsky R, Bowman DD, Geary TG, Prichard RK.

Abstract

Macrocyclic lactone (ML) endectocides are used as chemoprophylaxis for heartworm infection (Dirofilaria immitis) in dogs and cats. Claims of loss of efficacy (LOE) of ML heartworm preventives have become common in some locations in the USA. We directly tested whether resistance to MLs exists in LOE isolates of D. immitis and identified genetic markers that are correlated with, and therefore can predict ML resistance. ML controlled studies showed that LOE strains of D. immitis established infections in dogs despite chemoprophylaxis with oral ivermectin or injectable moxidectin. A whole genome approach was used to search for loci associated with the resistance phenotype. Many loci showed highly significant differences between pools of susceptible and LOE D. immitis. Based on 186 potential marker loci, Sequenom(®) SNP frequency analyses were conducted on 663 individual parasites (adult worms and microfilariae) which were phenotypically characterized as susceptible (SUS), confirmed ML treatment survivors/resistant (RES), or suspected resistant/loss of efficacy (LOE) parasites. There was a subset of SNP loci which appears to be promising markers for predicting ML resistance, including SNPs in some genes that have been associated with ML resistance in other parasites. These data provide unequivocal proof of ML resistance in D. immitis and identify genetic markers that could be used to monitor for ML resistance in heartworms.

Acute phase protein response in heartworm-infected dogs after adulticide treatment.

Vet Parasitol. 2015 Apr 30;209(3-4):197-201. doi: 10.1016/j.vetpar.2015.02.036. Epub 2015 Mar 12.

Méndez JC, Carretón E, Martínez-Subiela S, Tvarijonaviciute A, Cerón JJ, Montoya-Alonso JA

Abstract

During the adulticide treatment of Dirofilaria immitis the worms die releasing fragments of parasites and causing pulmonary thromboembolisms which could exacerbate the clinical condition. To determine the utility of acute phase proteins (APPs) to monitor the progression of the treatment, different positive [C-reactive protein (CRP), haptoglobin (hp)] and negative [albumin, paraoxonase-1(PON-1)] APPs were measured in 15 heartworm-infected dogs (5 with high and 10 with low parasite burden) following adulticide treatment. The results showed increased concentrations of CRP, decreased concentrations of haptoglobin and PON-1 in infected dogs before starting the treatment. Progressive but not significant increases were observed in PON-1 activity and albumin concentration along the treatment. After the treatment with doxycycline and ivermectine a decrease in CRP and Hp levels was experienced, which could reflect a reduction of the vascular inflammation caused by the elimination of Wolbachia and reduction of microfilariae. Fifteen days after the first melarsomine injection, marked increases in CRP and Hp were observed, which could be due to pulmonary inflammation and thromboembolism caused by the post-adulticide death of the worms. This increase was greater in dogs with high parasite burden. As the pathology disappeared, there was an improvement in the concentrations of CRP and Hp, returning into reference values in dogs with low parasite burden at the end of the treatment. The measurement of CRP and Hp could be a resource of support to evaluate the magnitude of the post-adulticide complications during the adulticide treatment of D. immitis.

Can the activation of plasminogen/plasmin system of the host by metabolic products of Dirofilaria immitis participate in heartworm disease endarteritis?

Parasites & Vectors 2015: 8 (1), 194.  doi: 10.1186/s13071-015-0799-0

J González-Miguel, R Morchón, E Carretón, JA Montoya-Alonso, F Simón.

Cardiopulmonary and inflammatory biomarkers in the assessment of the severity of canine dirofilariosis

Abstract

The prognosis and success of adulticide treatment depends on the baseline severity of infection with Dirofilaria immitis in dogs and can influence the therapeutic protocol to choose. A study was conducted to assess the utility of the cardiopulmonary biomarkers N-terminal of the prohormone brain natriuretic peptide (NT-proBNP), cardiac troponin I (cTnI), myoglobin, and D-dimer, as well as the biomarker of inflammation C-reactive protein (CRP) to evaluate the severity of canine heartworm disease in different stages. Serum samples were collected from 20 heartworm-infected dogs for measurement of these biomarkers. Dogs were assigned to four groups ( n= 5/group) according to the severity of the disease: Class I and Class II dogs showed concentrations of biomarkers generally within normal ranges for healthy dogs, except CRP in dogs classified as Class II, which showed values slightly above laboratory reference values (19.46. ±. 5.69. mg/l). Dogs of Class III showed elevated levels of NT-proBNP (1220.12. ±. 465.18. pmol/l) ( p<. 0.05), cTnI (0.99. ±. 0.39. ng/ml), CRP (33.98. ±. 7.99. mg/l) ( p<. 0.05), and 40% of these dogs (2/5) presented pathological values of D-dimer and myoglobin ( p<. 0.05). Dogs of Class IV (caval syndrome) presented elevated levels of NT-proBNP (>2530.8. pmol/l), cTnI (1.99. ±. 0.32. ng/ml), and CRP (80.24. ±. 47.69. mg/l); all Class IV dogs showed pathological elevations of D-dimer (0.81. ±. 0.46. ng/ml), and 60% (3/5) of these dogs showed pathological elevations of myoglobin (significant elevations [. p<. 0.05] for all biomarkers with respect to reference values and values for dogs in Classes I, II, and III). In canine heartworm disease, chronic presence of D. immitis causes a proliferative endoarteritis, thromboembolisms, pulmonary hypertension, and right-sided congestive heart failure. As the severity of the disease worsens, serum values of cTnI, myoglobin, and NT-proBNP increase, indicating significant cardiac damage. The finding of pathological concentrations of D-dimer suggests the presence of thromboembolism and/or disseminated intravascular coagulation. CRP increases according to the severity of the disease, indicating inflammatory processes that could contribute to the progression of the disease. These preliminary results demonstrate the utility of cardiopulmonary and inflammation biomarkers to assist in the establishment of the severity of canine heartworm disease.