A cohort study on anti-filarial IgG4 and its assessment in good and uncertain MDA-compliant subjects in brugian filariasis endemic areas in southern Thailand.

The prevalence of Brugia malayi was surveyed in three highly endemic provinces in southern Thailand as part of an ongoing evaluation of the effectiveness of two rounds of mass drug administration (MDA). Prior to MDA IV, and thereafter every 6 months up to 18 months, including MDA V at 12 months, nocturnal blood sampling was assayed for microfilaria (mf) and IgG4 antibodies in 200 subjects from Nakorn Srithammarat and Surathani provinces. From an additional 300 subjects from Narathiwatt province, daytime blood was also examined for IgG4 antibodies for 1 year. Subjects who tested positive, with reciprocal IgG4 titres above 100, were dichotomized in the 'good compliant' or 'uncertain compliant' groups. Stool samples were examined for intestinal parasites from all 500 subjects simultaneously. Only two subjects (1%) tested positive for mf, while 98 subjects (19.6% of 500) tested positive for IgG4. In general, the good drug-compliant subjects were less likely to exhibit the IgG4 response than subjects in the uncertain compliant group. Only six subjects (1.2%) exhibited lymphoedema while 68 subjects (13.6%) had a total of 105 parasitic infections, with female instances of protozoan infections exceeding male instances of helminth infections. It was concluded that the two MDA rounds were highly successful in not only in reducing mf to negligible levels but also in lowering antifilarial IgG4 titres in the good compliant subjects. The IgG4 assay is a sensitive and cost-effective surveillance tool for the early detection of brugian infections that is not contingent on nocturnal blood collections.

Bancroftian filariasis in a Philippine village: clinical, parasitological, immunological, and social aspects.

PIP: The distribution and effects of Bancroftian filariasis in 535 inhabitants of a Philippine village were investigated. Clinical, parasitiological, immunological, and socioeconomic assessments were made. A history of acute lymphatic inflammation and the presence of inguinal lymphadenopathy were common. Lymphatic obstructive disease, defined as leg edema, hydrocele, or an epididymal cyst, was more common in men than women and increased progressively with age. The prevalence and intensity of microfilaremia rose with age in males, whereas the prevalence but not the intensity of infection increased with age in females. The prevalence of immunological responsiveness, as assessed by skin reactivity to microfilarial antigen and serum antibodies to adult filarial worms, increased with age in both males and females. There was no relationship between either microfilaremia or obstructive disease and the ability to work or have children, but both were more common in heads of households with the lowest socioeconomic scores. Epidemiological factors which may have contributed to these findings are discussed. (author's modified)^ieng