A contribution to the diagnosis of Capillaria hepatica infection by indirect immunofluorescence test

Abstract

A highly specific pattern of immunofluorescence was noted when sera from Capillaria hepatica-infected rats were tested against the homologous worms and eggs present either in paraffin or cryostat sections from mouse liver. The pattern was represented by a combined apple green fluorescence of the internal contents of worms and eggs, which persisted in serum-dilutions of 1:400 up to 1:1600. Unequivocal fluorescent pattern was observed from 15 days up to 3 months following inoculation of rats with embryonated C. hepatica eggs and such result was confirmed by the ELISA. After the 4th month of infection, the indirect immunofluorescence test turned negative, probably revealing the extinction of parasitism, however the ELISA was contradictory, disclosing high levels of antibodies in this period. The IIF was also negative when control normal rat sera and sera from rats administered by gavage with immature C. hepatica eggs (spurious infection), or for reactions made against Schistosoma mansoni eggs, although a weakly positive pattern occurred with Fasciola hepatica eggs. The indirect immunofluorescence test may be recommended for use with human sera to detect early C. hepatica infection in special clinical instances and in epidemiological surveys, since it is a simple, inexpensive, and reliable test, presenting excellent sensitivity and specificity. Although the diagnosis is positive only during early infection, this is the period when the symptoms are usually more severe and the need for differential diagnosis is greater.

Capillariaisis (Trichurida, Trichinellidae, Capillaria hepatica) in the Brazilian Amazon: low pathogenicity, low infectivity and a novel mode of transmission

“…Maintenance of immunofluorescence at these dilutions is considered to be specific for Capillaria hepatica [19]. Of these, only 2 sera (one 4 years-old boy and one 34 years-old woman) remained positive after the dilution to 50% with PBS, thus characterizing a strong seroprevalence of only 0.81% among the sampled population.…”

“…An experimental study with Wistar rats [19] confirmed the excellent sensitivity and specificity of the indirect immunofluorescense technique and estimated that positivity starts 15 days after infection and lasts for three months. In false-positive cases (ingestion of non- embryonated eggs) reactions are initially positive; however, dilutions equal or greater than 1/400 show a negative reaction.…”

“…Serum samples were diluted in saline buffered solution (PBS) at 50% to 1/150 and tested against paraffin cuts containing mice livers with C. hepatica eggs and worms, according to the technique proposed previously [19]. The same author suggests a cut-off of 1/400 to diagnose false from- true-positive cases.…”

“…Results proved to be positive (>1/150) were scored as weak (PI), median (PII) and strong (PIII), based on fluorescence intensity, according to personal criteria of two different examiners. Nine of the 13 serum samples with median or strong reactions were further diluted to 1:500 and 1:1000 (higher than the cut-off level) in PBS and re-tested, in an attempt to exclude cases with unspecific fluorescence as suggested by Assis [19] The same technique was tested by Junker-Voss [20], who demonstrated a high specificity and sensibility to C. hepatica , with no cross-reactivity for serum samples of patients with documented infections of Echinococcus granulosus , E. multilocularis , Fasciola. hepatica , Schistosoma mansoni , Toxocara canis , Trichuris trichiura , and Trichinella spiralis .…”

Estudo da prevalência da Capillaria hepática (syn. Calodium hepaticum) em humanos e roedores em uma área urbana de Porto Velho, Rondônia, Brasil.

“… Em concordância com sugestão de Assis et al (2004), considerando a alta prevalência de infecção por C. hepatica de ratos nas grandes cidades e as más condições de higiene, que tantas vezes, prevalecem nos arredores das populações urbanas pobres, parece lógico suspeitar que as infecções humanas com este helminto possam ocorrer em tal ambiente. Um bom teste sorológico para o diagnóstico de infecção por C. hepatica poderia ser incluído no diagnóstico diferencial quando crianças ou mesmo adultos apresentarem hepatoesplenomegalia, febre inexplicável e eosinofilia.…”