Rapid decrease of precipitating and reaginic antibodies in Dirofilaria immitis-infected dogs which develop severe adverse reactions following treatment with diethylcarbamazine

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Immune responses of pony foals during repeated infections of Strongylus vulgaris and regular ivermectin treatments

Ten helminth-free pony foals divided into three groups were used in this study. Eight foals were each experimentally infected per os with 50 Strongylus vulgaris infective larvae weekly for 4 weeks, at which time one foal died of acute verminous arteritis. The remaining seven foals subsequently received 50 S. vulgaris infective larvae every 2 weeks for an additional 20 weeks. Four of the infected foals remained untreated (Group 1) and three of the infected foals were given ivermectin at 8, 16 and 24 weeks post initial infection (Group 2). Two foals served as controls (Group 3). Foals in Group 1 developed eosinophilia, which was sustained throughout the course of infection. A mild eosinophilia also developed in Group 2 foals; however, the eosinophil numbers were markedly reduced for 3 weeks after each ivermectin treatment. Only foals in Group 1 developed significant (P less than 0.05) hyperproteinemia, hyperbetaglobulinemia and a reversal of the albumin/globulin (A/G) ratio 4 weeks after initial infection. Significant (P less than 0.05) IgG anti-S. vulgaris ELISA titers developed in foals in Groups 1 and 2 3 weeks after infection and were sustained for the duration of the experiment. Western blot analysis of soluble somatic antigens of S. vulgaris adult female and male worms probed with sera from foals in Groups 1 and 2 revealed only subtle differences between these animals. The blastogenic reactivity of peripheral blood mononuclear cells (PBMC) to phytohemagglutinin and concanavalin A was not significantly different between groups. Peripheral blood mononuclear cells from foals in Groups 1 and 2 developed significant (P less than 0.05) blastogenic reactivity to S. vulgaris soluble adult somatic antigen when examined at 25 weeks after infection. Mesenteric lymph node cells from foals in Group 2, although not statistically significant, were more reactive to antigen than were the mesenteric lymph node cells from foals in Group 1 when examined at 27 weeks after infection. These results suggest that significant alterations in the immune response of ponies to S. vulgaris does not occur after intravascular killing of larvae by ivermectin treatments.

Heartworm infection

Dirofilaria immitis is an epizootic filarial parasite that most often infects domestic dogs. This article provides information about the life cycle of Dirofilaria immitis as well as the epidemiology, diagnosis, clinical signs, and treatment of heartworm infection.

Dirofilaria immitis: diethylcarbamazine-induced anaphylactoid reactions in infected dogs

The immunopathogenesis of the anaphylactoid Mazzotti reactions has been studied by comparing physiologic and immunologic aspects of diethylcarbamazine-induced shock in Dirofilaria immitis infected dogs with antigen induced anaphylaxis in infected and uninfected controls. Filarial antigen, specific host IgG antibody, and C1 and C3 complement levels were quantitatively measured over time in relation to the levels of histamine and prostaglandin D2 in the blood and changes in mean blood pressure. D. immitis antigen injected into uninfected dogs having no detectable IgG antibody to D. immitis or Toxocara canis produced a rapid drop in blood pressure that paralleled a drop in C1 and C3 levels and an increase in prostaglandin D2. Antigen injected into infected dogs with IgG antibody produced a similar drop in blood pressure and complement and increase in prostaglandin D2 which differed from the uninfected group only in the slower clearance of antigen from the blood. Diethylcarbamazine alone produced no measurable changes in blood pressure or complement in uninfected hosts. Diethylcarbamazine, however, administered into skin test positive infected dogs, produced a temporally slower but quantitatively similar loss in blood pressure, drop in complement, and increase in prostaglandin D2 and histamine to that induced by antigen injection. Complement activation and immune complex formation are initiated by antigen release, and subsequent vasoactive mediator release leads to shock with prostaglandin D2 being quantitatively higher in blood than is histamine.

Immunoglobulin interactions with surfaces of sheathed and unsheathed microfilariae

The sheath surface of Brugia pahangi microfilariae (mf) and the cuticle surface of Dirofilaria immitis mf were compared with regard to the ultrastructural arrangement of neutral and charged polysaccharides and binding of immunoglobulins from dog sera. Brugia pahangi: mf demonstrated large amounts of neutral sugar and negatively charged sugars just above the sheath surface, projecting some distance from the surface, in addition to a dense layer of sulphated material on the sheath surface. Microfilariae from high microfilaremic dogs showed no innately bound IgG or IgM when examined fresh from serum nor did they bind IgG or IgM from normal (NDS) or infected (IDS) dog sera after 48 h maintenance in RPMI 1640. Many of these mf did bind IgG and IgM from hyperimmune dog serum (ImDS) and these immunoglobulins were found binding at a distance from the sheath similar to that of the sugars. Dirofilaria immitis mf demonstrated much less neutral sugar at the cuticle surface, no negatively charged sugars and a diffuse, rather than dense, distribution of sulfated material extending from the cuticle. The majority of these mf showed innately bound IgG and IgM. After 48 h maintenance in RPMI 1640 D. immitis mf bound and shed IgG and IgM from NDS, high microfilaremia D. immitis IDS and D. immitis mf ImDS at distinctly different rates.

Immunopathology of parasitic diseases: a conceptual approach

These studies would indicate tremendous variations in the clinical manifestations of parasitic disease, resulting from characteristics of the parasite, the host, and their interaction. They further suggest that the conceptual mechanistic model described in the introduction is highly applicable. Previous evidence to substantiate the validity of such a model in schistosomiasis, a variety of protozoan diseases, and leprosy has already been presented (Phillips and Fox, 1982). This report would appear to lend additional credence to the postulates and suggests that upon scrutiny, the model represents a reasonable explanation for a wide variety of clinical manifestations of a parasitic disease. In addition, it may provide a working hypothesis for the interpretation of the immunopathology found in other diseases such as filariasis. Figure 3 compares and contrasts schistosomiasis and filariasis within the context of this hypothesis. Immunopathology results from the relative balance of host-parasite immunogenic factors and modulatory specific and nonspecific factors. The resultant immunopathology results from a number of immunologic mechanisms, but for the sake of comparison can be placed in certain analogous groups. Clearly, although a number of experimental questions still exist, vis-à-vis these analogies, it would appear that they are reasonable comparisons. It is hoped that such a conceptual approach might provide a useful framework for an understanding of the spectrum of immunopathology resulting from parasitic disease. These concepts might possibly lead to the eventual control of immunopathology.

Litomosoides carinii infection in cotton-rats before and after treatment with diethylcarbamazine and suramin: evolution of free serum antigens

Immunoelectrodiffusion was used to detect free serum antigens after treatment with diethylcarbamazine (DEC) and Suramin (S) in 30 cotton-rats infected with Litomosoides carinii. Precipitin lines between an antiserum produced by an adult worm extract and the test serum indicated the presence of free antigens in the serum. The number of precipitin lines was between one and 3. Before treatment only 13.3% of infected rats were positive compared with 83.7% after treatment. There was a difference in the delay before the appearance, the persistence and, possibly, the nature of antigens liberated by DEC and S treatment. With DEC release occurred earlier than with S and the antigens persisted for a shorter time. With combined DEC + S therapy the results were similar to those obtained with DEC and S used alone.