[Analysis of influencing factors of Trichuris trichiura infection in demonstration plots of comprehensive control of parasitic diseases]

OBJECTIVE

To understand the main risk factors of Trichuris trichiura infection in plots carrying out the integrated control of parasitic diseases.

METHODS

The simple and multiple unconditional logistic regression were applied to analyze related data from the database of baseline survey in demonstration plots carrying out the integrated control of parasitic diseases.

RESULTS

The results of simple logistic regression analysis suggested that the effects of 7 factors to Trichuris trichiura infection were significant (all P values were less than 0.05), namely drinking water resources, toilet type, fertilization type of farmland, fertilization type of vegetable field, washing hands after defecation, eating raw vegetables, melons and fruits and taking anthelminthic before examination. Among the factors above, eating raw vegetables, melons and fruits was of high risk (OR = 2.302), washing hands after defecation and taking anthelminthic before examination were two protection factors (with OR of 0.904 and 0.664, respectively). Compared to feces of human and livestock, fertilizing chemical fertilizer and compound fertilizer in farmland and vegetable field showed more obvious protection effect (with OR of 0.864 and 0.854, respectively). Drinking well water and spring water were two protection factors (with OR of 0.843 and 0.567, respectively). Simple toilet indoor and biogas pool also showed protection effect (with OR of 0.576 and 0.687, respectively). Multivariate analysis showed that four factors including eating raw vegetables, melons and fruits, fertilization type of farmland, fertilization type of vegetable field and taking anthelminthic before examination were determined to be the main influencing factors of Trichuris trichiura infection.

CONCLUSIONS

The main influencing factors of Trichuris trichiura infection in demonstration plots for the integrated control of parasitic diseases include eating raw vegetables, melons and fruits and fertilization type of farmland and vegetable field. Besides those, taking anthelminthic could reduce Trichuris trichiura infection of the population, meanwhile, sanitary water supply and latrine improvement could also reduce the risk of infection.

Earth-eating and reinfection with intestinal helminths among pregnant and lactating women in western Kenya

We conducted a longitudinal study among 827 pregnant women in Nyanza Province, western Kenya, to determine the effect of earth-eating on geohelminth reinfection after treatment. The women were recruited at a gestational age of 14-24 weeks (median: 17) and followed up to 6 months postpartum. The median age was 23 (range: 14-47) years, the median parity 2 (range: 0-11). After deworming with mebendazole (500 mg, single dose) of those found infected at 32 weeks gestation, 700 women were uninfected with Ascaris lumbricoides, 670 with Trichuris trichiura and 479 with hookworm. At delivery, 11.2%, 4.6% and 3.8% of these women were reinfected with hookworm, T. trichiura and A. lumbricoides respectively. The reinfection rate for hookworm was 14.8%, for T. trichiura 6.65, and for A. lumbricoides 5.2% at 3 months postpartum, and 16.0, 5.9 and 9.4% at 6 months postpartum. There was a significant difference in hookworm intensity at delivery between geophagous and non-geophagous women (P=0.03). Women who ate termite mound earth were more often and more intensely infected with hookworm at delivery than those eating other types of earth (P=0.07 and P=0.02 respectively). There were significant differences in the prevalence of A. lumbricoides between geophagous and non-geophagous women at 3 (P=0.001) and at 6 months postpartum (P=0.001). Women who ate termite mound earth had a higher prevalence of A. lumbricoides, compared with those eating other kinds of earth, at delivery (P=0.02), 3 months postpartum (P=0.001) and at 6 months postpartum (P=0.001). The intensity of infections with T. trichiura at 6 months postpartum was significantly different between geophagous and non-geophagous women (P=0.005). Our study shows that geophagy is associated with A. lumbricoides reinfection among pregnant and lactating women and that intensities built up more rapidly among geophagous women. Geophagy might be associated with reinfection with hookworm and T. trichiura, although these results were less unequivocal. These findings call for increased emphasis, in antenatal care, on the potential risks of earth-eating, and for deworming of women after delivery.

Trichuris vulpis recovered from a patient with chronic diarrhea and five dogs

We report a case of human infection with the whipworm of dogs, Trichuris vulpis, in a woman with duodenal ulcer disease, chronic diarrhea, and close contact with dogs. Morphologically, T. vulpis ova resemble those of the human whipworm (T. trichiura) but are nearly twice their size.

Interleukin (IL)-18 promotes the development of chronic gastrointestinal helminth infection by downregulating IL-13

Expulsion of the gastrointestinal nematode Trichuris muris is mediated by a T helper (Th) 2 type response involving interleukin (IL)-4 and IL-13. Here we show that Th1 response-associated susceptibility involves prior activation of IL-18 and caspase-1 followed by IL-12 and interferon (IFN)-gamma in the intestine. IL-18-deficient mice are highly resistant to chronic T. muris infection and in vivo treatment of normal mice with recombinant (r)IL-18 suppresses IL-13 and IL-4 secretion but does not affect IFN-gamma. In vivo treatment of T. muris-infected IFN-gamma-deficient mice with rIL-18 demonstrated that the inhibitory effect of IL-18 on IL-13 secretion is independent of IFN-gamma. Hence, IL-18 does not function as an IFN-gamma-inducing cytokine during chronic T. muris infection but rather as a direct regulator of Th2 cytokines. These results provide the first demonstration of the critical role of IL-18 in regulating Th cell responses during gastrointestinal nematode infection.

Trichuris Dysentery Syndrome: evidence that it may be underdiagnosed in Kelantan

The prevalence rate of trichuriasis in children in certain areas of Kelantan is high. However the Trichuris Dysentery Syndrome (TDS), a condition in children characterized by chronic diarrhoea, stunting and anaemia is said to be rare. A recent change in policy at our institution to lower the threshold for undertaking colonoscopy in children with chronic diarrhoea resulted in the detection of 6 cases of TDS in less than a year. The median age was 7 years (range 3-13) and the median duration of symptoms before diagnosis was 2 years (range 1-8). The insidious nature of TDS and the low level of awareness of this condition even among health care workers may result in considerable underdiagnosis.

Cryptic infection by whipworm mimicking a sessile polyp of the colon

A case of trichocephaliasis in a 70-year-old male is described. The original diagnosis, based on radiological and endoscopic findings, was of a sessile polyp of the colon. Only when a fragment of the supposed polyp was removed at biopsy and examined histologically was it revealed as a single male specimen of whipworm.

Interleukin-12 promotes a chronic intestinal nematode infection

Resistance and susceptibility to the intestinal parasite Trichuris muris has been shown to be due to a dominant T helper 2 (Th2) and a dominant Th1 response, respectively. The factors determining the initial polarization of the immune response remain largely unresolved, although the cytokine environment at the time of antigen presentation clearly plays an essential role. Interleukin (IL)-12, a cytokine produced mainly by macrophages, dendritic cells, and other monocytes has been shown to be important in driving a strong Th1 response by stimulating the production of interferon (IFN)-gamma from natural killer and Th0 cells and therefore forms a link between the innate and adaptive immune system. IL-12 has been shown to play an important role in resistance to a number of intracellular pathogens, including Listeria and Leishmania. It has also been proposed as an anti-tumor agent and for use in the treatment of HIV. Conversely, IL-12 has been shown to prolong the survival of Nippostrongylus brasiliensis and to accelerate autoimmunity. Our studies demonstrate that by driving a strong Th1 response, IL-12 promotes chronic T. muris infection when given to normally resistant BALB/K mice. Parasite-specific IgG2a, a Th1 parameter of infection, was greatly up-regulated, whereas some Th2 parameters of infection were down-regulated. IL-12 treatment could be delayed until 1 week after infection had started and still promote a strong Th1 response. The actions of IL-12 in promoting a chronic infection were IFN-gamma dependent as an anti-IFN-gamma mAb abrogated the effects of IL-12.

The pathogenesis of necrotic proliferative colitis in swine is linked to whipworm induced suppression of mucosal immunity to resident bacteria

Mucohemorrhagic enteritis syndrome in swine has a complex etiology with largely unknown pathogenesis. We have observed that inoculation of pigs with swine whipworm, Trichuris suis, initiates an interaction with resident bacterial flora to induce mucohemorrhagic enteritis. The role of bacteria in this mixed infection was demonstrated using 4 treatment groups. One group of pigs was inoculated with 2500 embryonated T. suis eggs alone, while a second group received T. suis eggs along with broad spectrum antibiotic treatment. Two other control groups of pigs were uninoculated and were either treated with antibiotic or untreated. Pigs inoculated with T. suis eggs exhibited diarrhea, mucosal edema, inflammatory cell infiltration, bacterial accumulation at the site of worm attachment in the proximal colon, and intestinal adenomatosis associated with the intracellular Ileal symbiont intracellularis bacteria. In addition, enlarged lymphoglandular complexes (LGCs) containing numerous extracellular bacteria, eosinophils, lymphocytes, macrophages, and neutrophils were observed in the distal colon. The other group of pigs that was inoculated with T. suis but treated with antibiotics had lesions localized to the site of worm attachment and histologically normal LGCs with no invasive bacteria in the distal colon. The groups of uninoculated pigs, with or without antibiotic treatment, exhibited no pathology or bacterial invasion. It appears that the complex pathogenesis of necrotic proliferative colitis in pigs may be linked to worm induced suppression of mucosal immunity to resident bacteria. Further, the association between bacteria,lymphocytes and macrophages in the LGCs of pigs infected with T. suis suggests an antigen-processing role for these structures in the colon. Further, the complex pathogenesis of necrotic proliferative colitis in pigs may be linked to worm induced suppression of mucosal immunity to resident bacteria.

Suppurative anal cryptitis associated with Trichuris trichiura. Report of a case

The whipworm (Trichuris trichiura) is an occasional finding in anorectal disease. All cases of anorectal discharge should include a test for ova and parasites. Trichuris infestations can be eliminated by the use of mebendazole (Vermox), a specific drug which has almost no side effects. It should be remembered that structural diseases of the anorectum, occurring during an infection such as fissure, fistula, and abscess, may persist after the infection has been cured and usually must be treated surgically.

The development and survival of Trichuris suis ova on pasture plots in the south of England

Pasture plots in the south of England were contaminated each month throughout 1975 with pig faeces containing Trichuris suis ova. At regular intervals thereafter, soil samples were taken, the T suis ova extracted and their state of development noted. Depending on the time of year that the plots were contaminated, ova required between 62 and 90 weeks to complete their development to the infective stage. Little or no development occurred during winter. Once the infective stage was reached, the ova survived for at least two years. Samples taken from the plots at various depths demonstrated that T suis ova did not rapidly leach through the soil but were still available to grazing pigs up to two and a half years later. The early developmental stages of ova appeared to be more susceptible to desiccation than those that had developed to the blastula stage or beyond.

[Infection of calves by Trichuris discolor]

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The stimulation of immunity to Trichuris muris in mice exposed to low-level infections

Mice infected with as few as ten eggs of the nematode Trichuris muris are highly resistant to a challenge infection given 5 weeks later. The rate of elimination of challenge larvae is similar in mice immunized by infection with ten or with 300 eggs. Stimulation of immunity to challenge by the low-level infections is dependent upon the persistence of the immunizing worm population and removal of the population at day 14 considerably reduces the level of immunity. Worms developing from a low-level immunizing infection are not eliminated by a ‘self-cure’ response, as is the case with larger infections, and become sexually mature. Adult worms from such an infection are, however, eliminated by the response to a superimposed challenge infection. Repeated infection of mice with small numbers of eggs stimulates an immune response and the worm population is eliminated before patency.