Electron and light microscopy of neutrophil responses in mice vaccinated and challenged with third-stage infective hookworm (Ancylostoma caninum) larvae.

The role of neutrophils in mediating host inflammation was examined in mice vaccinated with living third-stage infective hookworm larvae (L3). Mice were vaccinated by oral immunization with 500 L3 (Ancylostoma caninum) once every 2 weeks for a total of three immunizations. The vaccinated mice were then challenged intraperitoneally with 2000 L3) 1 week after the final immunization. To stimulate peritoneal production of neutrophils, 2 ml of 2% glycogen were injected intraperitoneally at 16 h prior to the challenge infection. Neutrophils were found to comprise 85% of the peritoneal cell population. L3 from the challenge infection were collected and then examined at timed intervals by inverted light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Greater than a fivefold increase in the total numbers of peritoneal cells was noted in the vaccinated mice as compared to unvaccinated mice. In the peritoneal cavity of vaccinated mice, the neutrophils adhered to the L3 within 2 h, and over 55% of the L3 were surround by clusters of neutrophils to form a sausage-like sheath 4 h later. At 24-72 h after challenge, almost all of the L3 recovered from the vaccinated mice were covered with thick clusters of cells. Both SEM and TEM demonstrated extensive ultrastructural damage to the L3. In contrast, the L3 recovered from the unvaccinated mice appeared to be unaffected by neutrophils. These studies suggest that neutrophils, like macrophages, can have an important role as effector cells in L3-vaccinated mice.

Epidemiology of human geohelminth infections (ascariasis, trichuriasis and necatoriasis) in Lushui and Puer Counties, Yunnan Province, China.

Between April and June of 1998, the prevalence and intensity of geohelminth infections caused by hookworm, Ascaris and Trichuris were investigated in two rural Yunnan villages. In Liuku, a village of Lisu indigenous people in Lushui County, there was an overall geohelminth prevalence of 72% (48%, 43% and 16% for hookworm infection, ascariasis, and trichuriasis, respectively). The prevalence of ascariasis was greatest among preschool and school aged children, whereas the prevalence of trichuriasis was greatest among teenagers and the prevalence of hookworm increased until the age of 10-15 and then remained high throughout adulthood. In Linger, a village of Han Chinese, located in Puer County, there was an overall geohelminth prevalence of 77% (30%, 60% and 36% for hookworm infection, ascariasis, and trichuriasis, respectively). The differences in prevalence for hookworm and ascariasis were statistically significant. The prevalence of hookworm in Linger increased steadily with age and did not plateau, but there were no discernible patterns of prevalence versus age for either ascariasis or trichuriasis. Heavy trichuriasis infections were noted to occur in Linger. In both villages, more than 98% of the hookworm infections were of light and moderate intensity. Both by morphologic identification of third-stage infective larvae (L3) from eggs as well as identification of adult hookworms recovered from adult residents after treatment with quantrel, Necator americanus was identified as the exclusive hookworm in each village. Geohelminth infections caused by Ascaris, Trichuris and hookworm remain highly endemic to the rural areas of Yunnan Province in southwestern China.

Epidemiology of human ancylostomiasis among rural villagers in Nanlin County (Zhongzhou Village), Anhui Province, China: II. Seroepidemiological studies of the age relationships of serum antibody levels and infection status.

Anti-hookworm antibody serologic responses were measured in residents of an Anhui provincial Chinese village where Ancylostoma duodenale is the predominant hookworm. Antibody responses were measured against either soluble infective third-stage larval (L3) or adult antigens. Immunoglobulins of the IgG class, especially IgG4 correlated with both the prevalence and intensity of A. duodenale hookworm infections. In contrast, there was an inverse correlation with IgM, but no correlation with IgA or IgE. Circulating IgG4 antibody responses might serve as a surrogate marker for active A. duodenale hookworm infection.

Epidemiology of human hookworm infections among adult villagers in Hejiang and Santai Counties, Sichuan Province, China.

Hookworm infection as well as other intestinal nematodiases are endemic to Sichuan Province in China. In order to research the prevalence and intensity of these infections we visited two villages in Hejiang County (southern Sichuan Province) and Santai County (northwestern Sichuan Province) between July and October of 1997. Fecal examinations were performed on adult villagers over the age of 15 years (currently children under this age are dewormed annually with anthelmintic drugs). Among 310 residents of Lugao Village (Hejiang County), 87, 63 and 60% were infected with hookworm, Ascaris or Trichuris, respectively. The prevalence of hookworm determined to rise linearly with age (r = 0.97). High intensity infections with hookworm still occur in this region as 22% of the residents have over 3000 eggs per gram (PEG) of feces as determined by quantitative egg counts. The majority of these individuals harbored mixed infection with Necator americanus and Ancylostoma duodenale, although the former predominated when adult hookworms were collected from 30 village residents treated with pyrantel pamoate. In contrast, among the 334 Xinjian villagers examined (Santai County) the majority harbored predominantly light hookworm infections--66.1% of the residents has less than 400 EPG by quantitative fecal examination and only 3.7% exhibited greater than 3000 EPG. Again, N. americanus was the predominant hookworm seen after worm expulsion. We have round that despite economic development which is occurring in some parts of China, significant hookworm infections and clinical hookworm anemia still exist in areas of Sichuan Province. In Hejiang County we found that the intensity of hookworm infection has actually risen within the last 10 years. Hookworm is a medical problem among the elderly in Sichuan.

Epidemiology of human ancylostomiasis among rural villagers in Nanlin County (Zhongzhou village), Anhui Province, China: age-associated prevalence, intensity and hookworm species identification.

Hookworm infection has traditionally been highly endemic to Anhui Province, China. Zhongzhou village in southwestern Anhui was identified as an endemic focus of infection caused by the hookworm Ancylostoma duodenale. This species was found to predominate over Necator americanus in ratios ranging from 35:1 based on the recovery of third-stage infective larvae (L,) to 21:1 based on the recovery of adult hookworms after anthelmintic chemotherapy. The overall prevalence of Ancylostoma infection in Zhongzhou was 33.2% with a greater prevalence among males. Unlike the age-associated prevalence patterns for N. americanus in Hainan and other southern Chinese provinces that show increasing prevalence with age and the highest prevalence among the elderly, the age-associated prevalence for A. duodenale in Zhongzhou exhibited a peak in middle-aged adults with subsequent decline. The age-associated intensity pattern exhibited a similar trend although the most of the hookworm infections were light or moderate infections as defined by quantitative egg counts.

Electron and light microscopy of peritoneal cellular immune responses in mice vaccinated and challenged with third-stage infective hookworm (Ancylostoma caninum) larvae.

The role of peritoneal macrophages in a murine model of immunity to living hookworm third-stage larvae (L3) was investigated. Mice immunized orally with 500 L3 once every 2 weeks for three times were challenged intraperitoneally with 2000 L3 1 week after the final immunization. The challenged larvae were collected from the peritoneal cavity at intervals between 2 and 72 h and then examined by inverted light microscopy, scanning electron microscopy and transmission electron microscopy. Peritoneal cellular responses in non-immunized mice served as negative controls. The numbers of peritoneal macrophages in immunized mice were 6-7-fold higher than in non-immunized mice. In the peritoneal cavity of immunized mice, host macrophages adhered to the challenged L3 within 2 h and created a cocoon-like encasing which surrounded the parasite. Extensive damage to the L3 was observed which included swelling, collapse and deformation of the larval cuticle. Lysis and vacuolization of the parasite's internal structures were also observed. In contrast, no significant cellular adherence and damage were observed in L3 recovered from non-immunized mice. L3-specific antibody levels were also elevated in the peritoneum of immunized mice relative to non-immunized controls. These studies implicate macrophages as important effector cells in hookworm larval vaccine immunity.

Epidemiology of human intestinal nematode infections in Wujiang and Pizhou counties, Jiangsu Province, China.

Intestinal nematode infections are considered highly endemic in the Chinese province of Jiangsu. In May 1997, the prevalence of intestinal nematodes infections was determined among all of the inhabitants aged 5 to 65 of the southern Jiangsu village of Yaojiakon (Wujiang County) and the northern Jiangsu village of Jianmiao (Pizhou County). It was determined that the prevalence of ascariasis, trichuriasis and hook worm infection was greatly reduced compared to when it was last measured in 1990. The reduction was noted to be particularly impressive in Yaojiakon village where the prevalence of ascariasis and trichiuriasis fell to 2% and 1.5% respectively. Much of this reduction was attributed to improvements in economic development which have occurred in southern Jiangsu Province at a rapid pace. In contrast, the reduction in nematode infections among villagers living in northern Jiangsu was more modest. The most striking reduction in both villages was in school-aged children who since 1988 have received yearly treatments with anthelminthic drugs. The intensity of nematode infections was investigated for hookworm where 70% of hookworm-infected Yaojiakon villagers were found to harbor light infections (< 400 eggs per gram) compared to 83% of hookworm-infected Jianmiao villagers. Necator americanus was the predominant hookworm in Yaojiakon village (South), whereas Ancylostoma duodenale predominated in Jianmiao village (North). The majority (76%) of hookworm-infected patients developed IgG antibodies against N. americanus antigen, although 20% of uninfected patients living in the village also had circulating antibodies. Intestinal nematode infections continue to be a significant public health problem in Jiangsu Province although their prevalence has decreased since 1990.

A recombinant protein from Schistosoma mansoni useful for the detection of S. mansoni and Schistosoma haematobium antibodies.

A recombinant Schistosoma mansoni protein has been identified as a useful antigen for the detection of S. mansoni and Schistosoma haematobium antibodies. The purified recombinant protein, Sm22.3, was assayed using an enzyme-linked immunosorbent assay format against a battery of 491 well defined sera, including S. mansoni, S. haematobium, and Schistosoma japonicum infection sera, normal human sera, sera from 9 other parasitic infections, and sera from 2 additional infections. The sensitivity for detecting S. mansoni and S. haematobium infections with this single recombinant protein is 80.1%. The specificity is 94.8%. However, 15 of the 16 cross-reactive sera are malaria infection sera, and we have data suggesting that these malaria sera are actually recognizing an epitope on the vector-derived 6Xhistidine tag of recombinant Sm22.3. If this is the case, then, the actual specificity of the assay is 99.6%.