Histological studies on praziquantel susceptible and insusceptible S. mansoni isolates

To study the biological differences of PZQ susceptible and insusceptible S. mansoni isolates; three S. mansoni isolates were studied in this work. The first one is the susceptible [Mo] isolate obtained from Egyptian villagers cured after a single oral dose PZQ [40 mg/kg]. The other two insusceptible isolates [Mt22, Mt24] were originally obtained from Egyptian villagers not cured alit three curative doses of PZQ,two doses of 40 mg / kg b.w followed by 60 mg/kg b.w This study revealed the lower PZQ efficacy on both insuceptible isolates [Mt22, Mt24] than on susceptible [Mo] isolate. Under the same circumstances the number of worm burden as well as their biological fitness [egg count/gm liver] were higher in both insusceptible isolates than susceptible one. Also, egg hatchability was low in both insusceptible isolates when compared with its absence in the susceptible one

Laboratory induced resistance to praziquantel in experimental schistosomiasis

To study the effect of praziquantel [PZQ] on successive generations of S. mansoni worms, infected mice were treated 6 weeks after infection with different doses of PZQ [300, 500 mg/kg], the schistosome strain was originally obtained from an infected Egyptian patient. The eggs subsequently produced by worms that had survived the PZQ treatment were used to infect snails and mice of the following generations. The results were expressed as average number of worms and cure rates in comparison with control groups. It was found that the use of PZQ, especially in low subcurative dose may lead to the development of resistance to therapeutic dose of the drug in following generations

Alternate chemotherapy in experimental schistosomiasis

Schistosoma mansoni infected mice were treated with a single oral dose of either praziquantel [400 mg/kg] or oxamniquine [100 mg/kg]. The uncured mice, after the first dose, were given a second dose of the same drug or alternatively with the other drug. The drug efficacy was monitored by stool examination and egg count using Kato-thick smear technique. Praziquantel was found to be more effective, it gave 60% cure rate after the first dose, increased to 100% after the second dose, than oxamniquine which had 37% and 74% cure rates, respectively. Furthermore, in uncured mice praziquantel resulted in more egg count reduction than oxamniquine. Treatment with the alternate drug of mice not cured with the first treatment gave 100% cure rate with praziquantel and 83% with oxamniquine. It was concluded that praziquantel is generally more effective than oxamniquine and cases not cured with a single dose of either drugs may be effectively treated with a second dose of the other

New trends in the sero-diagnosis of schistosomiasis in Egypt

A comparison has been made of a newly modified diffusion in-gel enzyme-linked immunosorbent technique [DIG-ELISA] 1 and an established, standerdized ELISA, using sera as well as whole blood adsorbed on filter paper discs. With known human cases of S. mansoni and/or S. haematobinum, both tests showed great sensitivity in the diagnosis of schistosomiasis; 93%-95% positive for ELISA and 92%-93% positive by DIG-ELISA on using egg antigens, while 92% positive for ELISA and 91% positive by DIG-ELISA when worm antigens were used. DIG-ELISA is characterised by its technical simplicity, high sensitivity which make it an excellent screening serological technique especially in endemic areas. Moreover, the use of whole blood on filter paper discs [paper disc DIG-ELISA], rather than serum from venipuncture should add more advantages for its field application

detection of IgE by radio allergosorbent technique [RAST] and elisa in Egyptian cases of schistosomiasis

Studies were carried out on the radioallergosorbent test [R.A.S.T.] in comparison with the Elisa for the diagnosis of schistosomiasis. Using sera from known S. mansoni, S. haematobium and both S. mansoni and S. haematobium cases, R.A.S.T. showed high sensitivity; 72%, 55% and 75% respectively, in the detection and quantification of specific IgE antibodies. While in case of ELISA only 20% of patients were positive. With control sera, both tests showed 100% negative. It is concluded that R.A.S.T. is more specific and superior than ELISA for IgE detection in schistosomiasis

status of schistosomiasis before and after treatment among school pupils in a village in the Nile Delta, Egypt

In a village in the Nile Delta, 452 out of 763, 9-16 years old school pupils were found infected with S. haematobium and/or S. mansoni. Males tended to have higher prevalence and intensity than females. There was also an increase in S. mansoni infections and a decrease in that of S. haematobium. These patients have been treated with a single oral praziquantel in dose of 40 mg/kg and followed up, for a period of one year. The cure rates, one or three months after treatment, were very high, especially in S. haematobium, whether single or mixed with S. mansoni infections. However, one year after treatment the re-infection rates were 18%, 10% and 1% for S. mansoni, S. haematobium or mixed infections, respectively. The cured and re-infected patients showed a decrease in the number of schistosome eggs than before treatment. The data were obtained in schistosome patients living in endemic area who received specific treatments. This could be explained according to the newly introduced hypothesis of blocking and protective antibody responses to egg antigens released from early and late infections of the child. However, a more extensive study with observations on transmission and water contact and with a greater range of immunological assays should be carried out in this endemic area

efficacy of praziquantel in Egyptian schistosomiasis

Three groups each consisting of 150 individuals were included. The first group included schistosomal patients receiving praziquantel. The second group included health individuals. The third group included schistosomal patients receiving no medication. Urine and stool examination were doing just prior to drug administration, one month and three months after medication. Although, after one month, cure rate was 100%, 80.7% and 98% for S. haematobium, S. mansoni and mixed infection, respectively; three months later the corresponding results were 61.5%, 67% and 98% in the same order. So, drug administration, even if effective, is not enough alone to control schistosomiasis in endemic areas

field trial of a new serological method for the diagnosis of schistosomiasis

Studies were carried out on a new serological method, diffusion in gel enzyme linked immunosorbant assay [DIG-ELISA] in comparison with two other techniques, thin layer immuno assay [TIA] and enzyme linked immunosorbant assay [ELISA] for the diagnosis of schistosomiasis. Using sera from known S. mansoni and /or S. haematobium cases, all tests showed great sensitivity in the detection and quantification of anti-schistosome antibodies. With sera from other helminth infections, DIG-ELISA and TIA produced small number of false positives, whereas ELISA gave none. DIG-ELISA and TIA are characterised by their technical simplicity, low costs and do not need any sophisticated equipment. Moreover, the well defined circular coloured reaction zones of DIG-ELISA are easily seen and measured. Improvement of the sensitivity and specificity of ELISA, TIA and DIG-ELISA could, however, be achieved by purification of the antigen used

effect of treatment on resistance to reinfection with schistosoma haematobium in hamsters and the measures of the anti-body levels by the elisa

Groups of five hamsters were infected with S. haematobium, treated at 17 weeks, reinfected at 24 weeks with different regimens and then were perfused at 35 weeks. Antibodies were measured every two weeks by the ELISA using different antigens. The results showed that: [i] hamsters reinfected 24 weeks showed 61% resistance [ii] chemotherapeutic eradication of the adult worms 17 weeks after the primary infection greatlyreduced the resistance seven weeks later;[iii] the antibody levels declined in response to treatment and was highly significant by the fifth week; [iv] antibodies detected by soluble egg antigen [SEA] are more than those detected either by adult worm antigen [AWA] or cercarial antigen; [v] the antibddy level rose in response to reinfection in the treated group and declined in the not reinfected group [vi] the antibody level did not rise in response to the reinfection in the group with primary infection and challenge, but showed a decline as in the group with primary infection only; this was more apparent with AWA than with SEA