Antibody and inflammatory responses in laying hens with experimental primary infections of Ascaridia galli.

Ascaridia galli, an intestinal nematode that affects hens and other domestic and wild birds, causes economic losses in avian exploitations. The present work shows that A. galli stimulates a strong antibody response as well as an intense inflammatory reaction, in the intestinal mucous of experimentally infected Lohmann Brown laying hens. IgG antibodies against soluble extracts of A. galli embrionated eggs and adult worms, were detected in both blood and yolks eggs from infected hens during a period of 105 days after the infection. This indicates that hens transfer to their offspring a part of the IgG antibodies produced when they become infected. The antigens responsible for the stimulation of specific IgG were molecules of 30-34, 44-54 and 58-90 kDa, while in the yolk eggs of infected hens a reactivity directed against antigens of molecular weight (M(w)) lower than 50 kDa was detected. Histology revealed traumatic lesions with leukocyte infiltration, and inflammation of the intestinal wall of the infected hens after 105 days of initial infection. The possible influence of the immune and inflammatory response on the population dynamics of the parasite is discussed.

Immunopathology of Dirofilaria immitis infection.

Heartworm disease caused by Dirofilaria immitis affects canine and feline hosts, with infections occasionally being reported in humans. Studies have shown that both dirofilarial antigens and those derived from its bacterial endosymbiont Wolbachia, interact with the host organism during canine, feline and human infections and participate in the development of the pathology and in the regulation of the host's immune response. Both innate and acquired immune responses are observed and the development of the acquired response may depend on the host and, or on its parasitological status. This review aims at illustrating current research on the role of both D. immitis and Wolbachia, in the immunology and immunopathology of dirofilariosis.

Immune response to and tissue localization of the Wolbachia surface protein (WSP) in dogs with natural heartworm (Dirofilaria immitis) infection.

Human and animal parasitic filarial nematodes, including the agent of canine and feline heartworm disease Dirofilaria immitis, harbour intracellular bacteria of the genus Wolbachia (Rickettsiaies). It is thought that these bacteria play an important role in the pathogenesis and immune response to filarial infection. Immunoglobulin G (total IgG, IgG1, IgG2) production against and immunohistochemical staining of tissues for the Wolbachia surface protein (WSP) from dogs with natural heartworm infection were evaluated. All infected dogs had significant total anti-WSP IgG levels compared to healthy controls. Interestingly, WSP was recognized by the IgG2 subclass in both microfilariemic dogs and in dogs with no circulating microfilariae (occult infection). However, microfilariemic dogs also produced gG1 antibodies. Positive staining for WSP was observed in lungs, liver and kidneys, in particular in glomerular capillaries of naturally infected dogs who had died from heartworm disease. Our results show for the first time that Wolbachia is recognized specifically by D. immitis--infected dogs and that the bacteria is released into host tissue. Furthermore, microfilariemic status appears to effect immune responses to this endosymbiont.

What is happening outside North America regarding human dirofilariasis?

The etiologic agents of human dirofilariasis in the Old World are Dirofilaria immitis, which cause pulmonary and subcutaneous nodules, and Dirofilaria repens, which cause ocular lesions. Although reports of new cases of dirofilariasis are sporadic in other parts of the world, a considerable amount of information is generated in Europe regarding human dirofilariasis. Most cases have been detected in the Mediterranean countries, Ukraine, and Russia; however, isolated or short series of cases have been reported in the Balkan Republics and central and northern European countries. Seroepidemiologic studies have provided evidence that humans living in endemic areas present rates of infection similar to those of the autochthonous canine populations. Antibodies against endosymbiont Wolbachia bacteria have been demonstrated recently in human Dirofilaria infections. During D. immitis infections, preadult worms and third- and fourth-stage larvae are often destroyed by the host reaction, releasing a considerable amount of Wolbachia, and a Th1-type response against Wolbachia and/or filarial antigens is mounted. On the contrary, infections with D. repens, in which worms frequently remain intact, no Th1-type response has been observed. As humans are resistant hosts, the Th1-response could have a role in the resistance against parasites. The causes for the rise in the incidence of human dirofilariasis as well as the possible application of Wolbachia antigens in the serodiagnosis of human infections are discussed.

Th1 response in BALB/c mice immunized with Dirofilaria immitis soluble antigens: a possible role for Wolbachia?

The immune response to filarial infection has been shown to be of both the Th1 and Th2 types. Studies aimed at developing immunization strategies against Dirofilaria immitis infection in dogs have shown that protection against larval challenge is of the Th2 type and that several proteins are recognized by immunized or infected animals. The bacterial endosymbiont Wolbachia, harbored by many filarial species including D. immitis, has recently been shown to interact with the host immune system. Specific antibodies to the Wolbachia recombinant surface protein (WSPr) have been observed in cats infected with D. immitis. In this work the authors have determined cytokine production and antibody response in BALB/c mice inoculated with soluble antigens from third stage larvae or from adult worms of D. immitis. Inoculated mice first produced IFN-gamma followed by a peak in IL-4. Specific antibodies to the Wolbachia protein WSPr were exclusively IgG2a, while antibodies against peptides derived from antigens of D. immitis were in the IgG1 and IgE subclasses. The cytokine response is thus similar to that reported for other filarial infection, where Th1 response shifts towards Th2. Antibody response indicates that Wolbachia may induce preferentially a Th1 response during filarial infection, while nematode antigens may be involved in Th2 response. There is thus an overall agreement with current opinions on the role of bacterial versus nematode molecules in driving the response towards the different directions.

A coprological and serological survey for the prevalence of Ascaridia spp. in laying hens.

Ascaridia galli is a common nematode found in the intestine of domesticated chickens. The objectives of the study were to conduct a coprological and serological survey on the prevalence of ascaridiosis in laying hens of commercial farms. The farms recently adopted a breeding programme, where the hens have access to outdoor pens. Different amounts of Ascaridia eggs were detected in five of seven studied farms, while the other two farms were found to be free from the parasite. Serological tests revealed a seroprevalence of 21.8% (range 7.6-95%). No positive serum samples were detected in the same farms with previous negative coprological analysis. Western blot analyses confirmed the results obtained by the enzyme-linked immunosorbent assay (ELISA) test. In four experimentally infected hens, a progressive increase of the IgG antibody levels was observed, surpassing the cut-off point established for ELISA test 6 weeks post-infection. Serological tests are able to detect the infection before the eggs of the parasite appear in the faeces of infected hens, providing a useful tool to detect infections with Ascaridia spp. in avian farms.