Serum protein electrophoresis in Dirofilaria immitis naturally infected dogs: Latest news and a systematic literature review

According to the main Guidelines on canine heartworm disease (HWD) by the American and European Societies (i.e., AHS, ESDA, and ESCCAP), a correct diagnosis of Diroffictria immitis infection should include the detection of circulating microfilariae in the whole blood and the adult antigens in serum or plasma sample. So far, scant data are available on laboratory abnormalities in dogs affected by HWD, although techniques including serum protein electrophoresis (SPEP) have proved to be useful for the diagnosis and monitoring of other vector-borne diseases, such as the canine leishmaniosis. Therefore, this study aims to evaluate the SPEP pattern in dogs naturally infected by D. immitis. Furthermore, a systematic review of the literature on this topic was carried out. Medical records from heartworm-positive dogs, of any sex, age, and breed and with available clinical examination and laboratory test results (i.e., complete blood count, serum biochemical profile, and SPEP) were retrospectively collected. If available, laboratory results obtained from dogs after treatment for HWD were also evaluated. When compared with the reference intervals, out of 30 dogs infected by D. immitis and enrolled, 63.3% (n = 19) had a lower percentage of albumin, and 80.0% (n = 24) had higher percentages of beta globulins, with beta-2, and especially beta-3 globulins the most frequently altered fractions. In terms of absolute values (g/dL), the proportion of dogs with hypoalbuminemia, and increased total globulin, alpha, beta- and gamma globulins were 4/30 (13.3%), 6/30 (20.0%), 2/30 (6.7%), 16/30 (53.3%) and 8/30 (26.7%), respectively. For 7 dogs, SPEP results evaluated three and six months after treatment with doxycycline (10 mg/kg BID for 4 weeks) were available. In these dogs a significant post-treatment increase in the percentage of albumin, alpha-2 globulin, and albumin/globulins ratio was observed, as well as a significant decrease both in the percentage and in the absolute value of total-, beta-, and beta-3 globulins. The systematic review of literature databases yielded a total of three studies that were considered eligible and included in the qualitative synthesis. This study provides novel information on SPEP alterations in dogs naturally infected by D. immitis. The evaluation of serum proteins and their electrophoretic pattern may represent an important diagnostic tool for a prompt and accurate diagnosis (e.g., differentiating infections in dogs sharing similar clinical signs and endemic in the same geographical area) and monitoring of HWD.