The clearance effect of bovine anti-Helicobacter pylori antibody-containing milk in O blood group Helicobacter pylori-infected patients: a randomized double-blind clinical trial.

BACKGROUND: The failure in standard triple therapy has recently increased to high levels in China, primarily because of insufficient patient compliance, antimicrobial resistance, and high costs. Effective prevention and eradication of Helicobacter pylori (H. pylori) by artificial passive immunization with orally administered bovine antibodies in the milk has been demonstrated in many animal studies, but the clinical studies that are available have shown no H. pylori eradication. This study was to evaluate the efficacy and safety of orally administered bovine anti-H. pylori antibodies for the clearance of H. pylori infecting O blood group subpopulations. METHODS: Two local epidemic H. pylori strains that were prevalent locally were screened and then used to immunize dairy cows. After confirmation of the presence of anti-H. pylori polyclonal antibodies in the milk by enzyme-linked immunosorbent assay, the milk was subsequently defatted and processed into sterile milk by pasteurization. This study was designed as a double-blind placebo-controlled randomized clinical trial. Our 61 H. pylori-infected O blood group subjects were assigned to two groups; 31 subjects were treated with bovine milk containing antibodies and 30 subjects with the placebo. The medication-based study was continued for 28 days. Subjects were followed up for 56 days. The effect was assessed by the C-14 urea breath test (UBT). SPSS 17.0 software for Windows was used to analyze the data. RESULTS: Of the 61 subjects enrolled, 58 completed the protocol. One volunteer in the antibodies group and two volunteers in the control group dropped out. Of the 30 antibody-treated subjects, 13 became UBT negative, whereas none of the 30 of the placebo-treated subjects became UBT negative after the medication. Of 13 UBT negative patients, 3 became positive again at the end of the follow-up. Both intention to treat and per-protocol analysis indicated a significant difference in the clearance rate of infected patients between the groups treated with bovine antibody-containing milk and the placebo (P = 0.001, P < 0.05) and no significant difference in adverse effects (P > 0.05 all). CONCLUSIONS: Bovine antibody-based oral immunotherapy appears to be safe and has a significant clearance effect on intragastric H. pylori that infects O blood group adults. TRIAL REGISTRATION: ChiCTR-TRC-14005212.

[In vitro effect of seven anthelmintic agents against adult Clonorchis sinensis].

OBJECTIVE: To observe the in vitro effect of praziquantel, tribendimidine, levamisole, artemether, artesunate, albendazole and mebendazole against adult Clonorchis sinensis. METHODS: Seventy rats infected with 50-100 C. sinensis metacercariae for 5-7 weeks were euthanized, and adult C. sinensis were collected from the common bile duct Three to four worms were placed in each well of a 24-well falcon plate, and treated by Hanks' balanced salt solution-20% calf serum containing aforementioned drugs at various concentrations. The motor activity and morphology change of the worms were observed under an inverted microscope at 4, 24, 48 and 72 h post treatment. RESULTS: Praziquantel could reduce the motor activity of the worms rapidly which resulted in detachment of oral sucker from the well wall, curl of the worm body and emergence of vacuoles from the tegument. The minimal concentration of praziquantel to kill adult C. sinensis was 0.1 g/ml. After adult C. sinensis exposed to tribendimidine at concentrations of 0.5, 1 and 10 g/ml, they revealed in paralysis, looseness and stretch of the worm body rapidly or immediately. The minimal concentration of tribendimidine to kill adult worms was 0.05 g/ml. When worms exposed to levamisole at 10 and 20 g/ml, there was a gradual decrease in the worm's motor activity accompanied by looseness of the worm body. But 48 h post exposure, most worms showed apparently recovery of motor activity. In a higher levamisole concentration of 50 g/ml, all worms revealed in stretch and paralysis which was similar to that induced by tribendimidine. When adult C. sinensis were exposed to artemether or artesunate 10 and 50 g/ml, the motor activity of worm body and oral sucker reduced which accompanied by worm contraction, then followed by looseness of the worm body and emergence of vacuoles along the tegument. At 72h post exposure, the worm mortalities induced by the two concentrations of the two drugs were about half, respectively. In adult C. sinensis exposed to albendazole and mebendazole at concentrations of 10 and 50 g/ml, only stimulation of motor activity of oral sucker was seen which revealed in vigorous contraction within 24 h post exposure. During 72 h observation period, no any other changes in worm activity and morphology were seen. CONCLUSION: Praziquantel and tribendimidine exhibit strong in vitro killing effect on adult C. sinensis. The minimal concentration of levamisole used to kill adult worm is 50 times higher than that of tribendimidine. The higher concentrations of artemether and artesunate show slower action to reduce the worm activity and kill part of the worms. Higher concentrations of albendazole and mebendazole exhibit no killing effect on C. sinensis, besides stimulating the motor activity of worm oral sucker.

Comparative effect of mebendazole, albendazole, tribendimidine, and praziquantel in treatment of rats infected with Clonorchis sinensis.

The aim of the study is to understand the anti-Clonorchis sinensis properties of mebendazole and albendazole, and compare to praziquantel and tribendimidine. Two hundred and thirty rats were divided into five batches for experimental treatment. In four batches, each rat was infected orally with 50 or 100 C. sinensis metacercariae. Twenty-eight to 46 days post-infection, groups of rats were treated orally with single doses of mebendazole, albendazole, praziquantel, tribendimidine, or multiple daily doses of albendazole. While in the remaining batch, mebendazole or praziquantel was administered to groups of rats infected each with 50 metacercariae for 7 or 14 days. In each batch of test, untreated but infected rats served as control. All rats were euthanized 2-4 weeks post-drug administration for assessment of efficacy. In the first batch of test, rats treated with mebendazole or tribendimidine at single doses of 150, 75, and 37.5 mg/kg resulted in worm burden reductions of 99.0%, 94.0%, and 73.1%, or 98.0%, 80.6%, and 60.4%, respectively. When rats were treated with albendazole at the same dose levels, no or poor effect was seen. In the second batch of test, promising effect against adult C. sinensis in rats treated with mebendazole or tribendimidine at single doses of 100 and 50 mg/kg were also observed, but under the single dose of 25 mg/kg, only tribendimidine still remained the effect. In the third batch of test, the aforementioned three single dose levels of mebendazole, albendazole and praziquantel were applied. Again, mebendazole exhibited higher effect and albendazole exhibited no or poor effect. While praziquantel, administered at a higher dose of 300 mg/kg, also showed promising effect. In the fourth batch of test, oral administration of albendazole at a daily dose of 150 or 100 mg/kg for 2 or 3 days resulted in moderate or higher efficacy with worm burden reductions of 79.2% and 91.9%, respectively. In the fifth batch of test, single mebendazole doses of 150 or 75 mg/kg exhibited promising effect against 14-day-old C. sinensis in rats with worm burden reductions of 95.3% and 86.4%, respectively, but mebendazole was short of the effect against 7-day-old worms. Under the same dose level, praziquantel possessed an effect against both 7- and 14-day-old juvenile C. sinensis. The results confirm that in infected rats, mebendazole administered orally at a single dose of 150 mg/kg exhibits potential effect against juvenile (14-day-old) and adult C. sinensis. No or less effect is obtained from albendazole under the same dose levels, but extension of treatment course may enhance the effect of albendazole against this species of fluke. The single effective dose ranges of mebendazole and tribendimidine against C. sinensis in rats are similar with a broad window, while the window for praziquantel is narrow.

[Effect of six anthelmintics in oral treatment of mice infected with Armillifer agkistrodontis nymphs].

OBJECTIVE: To observe the effect of praziquantel, mebendazole, tribendimidine, ivermectin, artemether and dihydroartemisinin against Armillifer agkistrodontis nymphs harbored in mice. METHOD: Thirty-five mice infected each with 40 eggs of Armillifer agkistrodontis for 25-37 weeks were divided into 10 groups (2-8 mice per group). Among them, nine groups were treated orally with praziquantel 500 mg/(kg x d) x 5 d or 500 my/(kg x d) x 14 d, mebendazole 300 mg/(kg x d)x 5 d, tribendimidine 300 mg/(kg x d) x 5 d, ivermectin 8-10 mg/(kg x d) x 3 d or 15 mg/(kg x d) x l4 d, artemether 400 mg/(kg x d) x 5 d and dihydroartemisinin 200 mg/(kg x d) x 5 d, respectively. The remaining untreated group served as control. All mice were sacrificed 1-3 weeks post-treatment for collection and separation of Armillifer agkistrodontis nymph cysts from abdominal wall, lipid tissue and viscera including liver, spleen and outer wall of intestine. The nymphs were released after tearing up the cyst with forceps, placed in the normal saline to observe their motor activity and counted. RESULTS: The difference of mean nymph burden between the drug treated groups and control group was not statistically significant (P > 0.05) with mean nymph reductions of 8.3%-35.0%. Meanwhile, the appearance of the cyst, the size, colour, morphology and motor activity of nymphs were also similar to that of the control. CONCLUSION: Praziquantel, mebendazole, tribendimidine, ivermectin, artemether and dihydroartemisinin exhibit no effect against Armillifer agkistrodontis harbored in mice under the conditions in the experiment.

[Treatment of rats infected with Clonorchis sinensis using clinical administration regimens of tribendimidine, praziquantel and artesunate].

OBJECTIVE: To evaluate the efficacy in treatment of Clonorchis sinensis-infected rats using the administration regimens of tribendimidine, artesunate and praziquantel applied in clinical treatment of clonorchiasis. METHODS: The doses of tribendimidine, artesunate and praziquantel used in clinical treatment of clonorchiasis were converted to the doses used in rats by the method of equal effective dose conversion among different animals, while the administration regimens of the drugs were designed basing on the regimens used in clinical trials. Thus, the following dose schedules were set up, i.e., tribendimidine 16 or 32 mg/(kg x d) x 1, 2 or 3 d (bid), 8 or 16 mg/(kg x d) x 3 d; artesunate 12 mg/(kg x d) x 3 d (tid) and 16 mg/(kg x d) x 3 d (bid); praziquantel 143 mg/(kg x d) x 2 or 3 d (tid), 143 mg/(kg x d) x 2 or 3 d (bid), 47.7 or 71.5 mg/(kg x d) x 3 d. 151 rats were divided into 2 batches and each rat was infected orally with 50 metacercariae of C. sinensis. In the first batch of test, 79 rats were divided into 13 groups of 5-6 rats 5 weeks post-infection. Among them 6 groups were treated orally only with tribendimidine, artesunate or praziquantel, while other 7 groups were treated with tribendimidine combined with artesunate or praziquantel, or praziquantel combined with artesunate. The remaining 8 untreated rats served as control. In the second batch of test, 72 rats were divided into 13 groups of 5 rats. Among them, 7 and 6 groups were treated with tribendimidine and praziquantel, respectively, 6 weeks post-infection. The remaining 8 untreated rats served as control. Rats were sacrificed 14 days post-treatment, worms were recovered from the bile duct and the liver tissue. The mean worm reduction rate was calculated and compared among the groups by non-parametric method (Mann-Whitney test). RESULTS: In the first batch of test, the mean worm burdens in rats infected with C. sinensis and treated orally with tribendimidine 16 or 32 mg/(kg x d) x 3 d (bid), praziquantel 143 mg/(kg x d) x 3 d (tid), or 143 mg/(kg x d) x 3 d (bid) were significantly lower than that of the control (P < 0.01) with mean worm burden reductions of 94.2%-96.0%. No efficacy was seen when infected rats were treated orally with artesunate 12 mg/(kg x d) x 3 d (tid). But in those treated with artesunate 16 mg/(kg x d) x 3 d (bid), the mean worm burden was significantly lower than that of the control (P < 0.05) with a mean worm reduction of 57.2%. In combined treatment, the infected rats treated with tribendimidine 16 or 32 mg/(kg x d) x 3 d (bid) in combination with praziquantel 143 mg/(kg x d) x 3 d(bid) or artesunate 16 mg/(kg x d) x 3 d (bid), the difference of mean worm burden between each combined treatment group and control group was statistically significant (P < 0.01) with mean worm reductions of 94.2% -99.4% which revealed that the worm reduction rate in combined treatment group was similar to the corresponding group treated with tribendimidine or praziquantel alone, but significantly higher than that of the group treated with artesunate alone. In infected rats treated with praziquantel 143 mg/(kg x d) x 3 d (tid) plus artesunate 12 mg/(kg x d) x 3 d (tid) or praziquantel 143 mg/(kg x d) x 3 d (bid) plus artesunate 16 mg/(kg x d) x 3 d (bid), the mean worm burden reductions were 93.6% -100%. In the second batch of test, the efficacy of tribendimidine obtained from infected rats treated with the drug 16 or 32 mg/(kg x d) x 2 d (bid) and 3 d (bid), the difference of mean worm burdens between them was not statistically significant with mean worm reductions of 86.5%-95.1%. When rats were treated with tribendimidine 32 mg/(kg x d) x 1 d (bid), the mean worm reduction was 73.0%, while the dose of the drug was given to the rats at 8 or 16 mg/kg daily for 3 days the mean worm reduction rates were 88.3%-92.6%. Treatment of praziquantel 143 mg/(kg x d) x 3 d (tid) resulted in a worm reduction of 96.9%, if the treatment course reduced to 2 d, the rate was 63.2%. Similar results were obtained in rats treated with praziquantel 143 mg/(kg x d) x 2 d (bid) and 3 d (bid). Finally, administration of praziquantel at a daily dose of 47.7 or 71.5 mg/kg for 3 d exhibited no effect against C. sinensis. CONCLUSION: When the dose schedules of tribendimidine, artesunate and praziquantel used in humans are converted to the doses for use in rats, tribendimidine and praziquantel exhibit satisfactory effect against C. sinensis, but artesunate shows no or less effect; the treatment course of tribendimidine can be reduced from 3 d to 2 d. Since tribendimidine and praziquantel used alone have endorsed high efficacy against C. sinensis in rats, combinations among the 3 drugs do not show better effect.

[Efficacy of tribendimidine and albendazole in treating mice infected with Trichinella spiralis].

OBJECTIVE: To observe the efficacy of tribendimidine and albendazole against Trichinella spiralis in mice. METHODS: A total of 85 Kunming strain mice, infected orally with 100 T. spiralis larvae, was divided into 3 groups: group A (adult stage, 7 d after infection), group B (migrating larva stage, 15 d after infection), and group C (encapsulated larva stage, 35 d after infection). Group A (35 mice) was equally divided into 7 sub-groups, tribendimidine and albendazole were each orally administered to 3 sub-groups both with doses of 6.25, 12.5, and 25 mg/kg respectively, the untreated sub-group served as control. Groups B and C (25 mice each) were both divided equally into 5 sub-groups. Mice in 2 sub-groups were treated respectively with the 2 drugs in a dose of 100 or 200 mg/kg, the untreated sub-group served as control. Mice in group A were sacrificed 2 d post-treatment and adult worms recovered from the small intestine were counted. Those in groups B and C were sacrificed 15 d post-treatment and intact diaphragm was then removed from each mouse. The muscle of diaphragm was digested by digestive solution and the larvae were counted by stereomicroscope. Mean worm burden and mean worm reduction of each treated group were calculated and statistically compared with the control. RESULTS: The mean worm burden in sub-groups of group A treated with tribendimidine was significantly lower than that of the control (P<0.01) with a mean worm reduction of 63.3%, 86.2%, and 98.5%, respectively. In the same batch of mice treated with albendazole at a single dose of 6.25 and 12.5 mg/kg resulted in similar mean worm burden compared to the control (P<0.05). While in the sub-group received albendazole at a higher dose of 25 mg/kg, the mean worm burden was significantly lower than that of the control (P<0.05), with a mean worm reduction of 41.2%. The mean worm burden in group B was significantly lower than that of the control (P<.01). The mean worm reduction in the 2 sub-groups treated with tribendimidine or albendazole was 64.4% and 89.6%, or 56.7% and 78.4%, respectively. In group C, significantly lower mean worm burden was only found in the subgroup treated with albendazole at a higher dose of 200 mg/kg than the control (P<0.01) with a mean worm reduction of 71.8%. No effect was seen in the other 3 groups. CONCLUSION: Tribendimidine exhibits potential effect against adult and migrating larva stage of T. spiralis in mice, but lacks effect against encapsulated larva stage of the parasite. Albendazole administered at a larger or multiple doses to mice endorses effect against its adult, migrating larva and encapsulated larva stages.

[Therapeutic effect of tribendimidine, artesunate and praziquantel administered to hamsters infected with Clonorchis sinensis].

OBJECTIVE: To observe the effect of tribendimidine, artesunate and praziquantel in treatment of hamsters (Mesocricetus auratus) infected with Clonorchis sinensis. METHODS: A total of 93 hamsters, each infected with 30 C. sinensis metacercariae, were treated intragastrically with above-mentioned drugs at a single dose. (1) In order to observe the effect of the drugs against juvenile C. sinensis, 20 out of 31 infected hamsters were randomly divided into 4 groups (5 hamsters per group) 14 d post-infection: artesunate 300 mg/kg, tribendimidine 100 mg/kg or 200 mg/kg, and praziquantel 200 mg/kg. Other 6 hamsters were divided equally into 2 groups 24 d post-infection and treated with tribendimidine 200 mg/kg and artesunate 300 mg/kg, respectively. The remained 5 untreated hamsters served as control. (2) Twenty-two hamsters were randomly divided into 5 groups (4-5 hamsters per group) 28 d post-infection and treated with tribendimidine 25 mg/kg or 50 mg/kg, artesunate 25 mg/kg and praziquantel 50 mg/kg, respectively. Other untreated hamsters served as control. (3) Forty hamsters 28 d after infection were randomly divided into 8 groups (4-6 hamsters per group) and treated with tribendimidine 50 mg/kg, 100 mg/kg or 200 mg/kg, artesunate 100 mg/kg or 200 mg/kg, praziquantel 100mg/kg or 200mg/kg, respectively. The remained hamsters served as control. All hamsters were sacrificed 14 d post-treatment and worms were recovered from the bile duct and liver tissue. The mean worm burden and its reduction were calculated. The differences of mean worm burden between each treated group and the corresponding control were analyzed statistically. RESULTS: In hamsters infected with 14-d-old C. sinensis and treated orally with tribendimidine at a single dose of 100 or 200 mg/kg, the mean worm burdens were significantly lower than that of the control (P<0.01) with a worm reduction of 90.6% and 85.9% respectively. The mean worm burden obtained from the infected hamsters treated with praziquantel at a single dose of 200 mg/kg was also significantly lower than that of the control (P<0.05) with a worm reduction of 71.9%. However, the difference of mean worm burden between artesunate and control groups was not statistically significant. The juvenile parasites developed into adult worms 24 d after infection. By administering tribendimidine 200 mg/kg to the adult C. sinensis-infected hamsters, the mean worm burden was significantly lower than that of the control (P<0.01) with a worm reduction of 89.8%. Whilst the administration of artesunate at a higher dose of 300 mg/kg, all hamsters were cured. Further tests indicated that tribendimidine in a lower dose of 25 mg/kg to the hamsters 28 d after infection resulted in a significantly lower mean worm burden compared to the control (P<0.05) with a worm reduction of 71.8%. With an increased dose of tribendimidine 100 mg/kg, all hamsters were cured. The worm reduction was only 20.0% and 56.4% when 25 mg/kg and 100 mg/kg of artesunate were administered. With 200 mg/kg artesunate, the worm reduction reached as high as 98.5% and the mean worm burden was significantly lower than that of the control (P<0.01). Furthermore, administration of praziquantel at a dose of 100 mg/kg or 200 mg/kg at 28 d post-infection resulted in a significantly lower mean worm burden than that of the control (P<0.05) with a worm reduction of 78.9% and 83.5% respectively. CONCLUSION: In hamster model, tribendimidine and praziquantel exhibit promising effect against both juvenile and adult C. sinensis, while artesunate is only efficacious against adult worms.

The in vitro and in vivo effect of tribendimidine and its metabolites against Clonorchis sinensis.

The purpose of the study was to understand the in vitro and in vivo effect of tribendimidine (TBD) and its metabolites of p-(1-dimethylamino ethylimino)aniline (aminoamidine, deacylated amidantel, BAY d 9216, dADT), acetylated dADT (AdADT), terephthalaldehyde (TPAL), and terephthalic acid (TPAC) against adult Clonorchis sinensis. In in vitro test, the adults of C. sinensis were placed to each of the 24 wells of a Falcon plate and maintained in Hanks' balanced salt solution-20% calf serum. Besides observation on the direct in vitro effect of TBD and its metabolites, the worms exposed to TBD and its metabolites for 1-24 h were transferred to the medium without drug and incubated continually for another 72 h. The reversible effect of TBD and its metabolites was assessed by the recovery of worm motor activity and parasite survival. In in vivo test, 235 rats were divided into five batches for oral infection of each rat with 50 C. sinensis metacercariae. Five to 6 weeks post-infection, groups of rats were treated orally or intramuscularly with a single dose of TBD or its metabolites, while untreated but infected rats served as control. All treated rats were killed 2 weeks post-treatment for assessment of efficacy. When adult C. sinensis were exposed to TBD or dADT 0.5 microg/mL, they were paralyzed rapidly accompanied by dilatation of the gut. The in vitro effect of AdADT decreased significantly, which was at least lower than 20- to 40-fold compared with TBD and dADT. TPAL and TPAC at a high concentration of 100 microg/mL exhibited no effect against adult C. sinensis. In the worms exposed to TBD or dADT 1 microg/mL for 1 h, well recovery of the worm motor activity from paralysis was seen in the medium without drug. If exposure time extended to 4-24 h before transferred to the medium without drug, few worms were dead and most worms showed very poor recovery of their activity. When the worms exposed to TBD or dADT 10 microg/mL for 1, 4, and 24 h were transferred to the drug-free medium, recovery of poor motor activity of worms or worm death was seen. In the worms exposed to AdADT 20 and 40 microg/mL for 1-24 h, more worms recovered poor motor activity in the medium without drug. In rats infected with C. sinensis and treated orally with TBD or dADT, the ED(50) and ED(95) were 20.318 and 195.358 mg/kg or 18.969 and 268.882 mg/kg. Under the equal dosages used in the treatment of rats infected with C sinensis, the effects between TBD and dADT or TBD and AdADT were similar. Intramuscular TBD or dADT at a single dose of 12.5-75 mg/kg showed effect against adult C. sinensis harbored in rats. TPAL and TPAC exhibit no effect against C sinensis harbored in rats treated orally with a higher dose of 1 g/kg. The results indicate that TBD and dADT exhibit a strong in vitro effect to paralyze the adult C. sinensis, but less in vitro effect was seen in AdADT. TBD, dADT, and AdADT exhibit similar therapeutic effect in oral treatment of rats infected with C. sinensis, and intramuscular TBD and dADT also show promising effect against C. sinensis in rats. TPAL and TPAC are ineffective metabolites of TBD.

[Effect of tribendimidine, artesunate, artemether and praziquantel, administered intragastrically at single, multiple or combined doses, to rats infected with Clonorchis sinensis].

OBJECTIVE: To assess the efficacy of single, multiple or combined oral doses of tribendimidine, artesunate, artemether and praziquantel against Clonorchis sinensis in rats. METHODS: A total of 147 rats, each infected with 50 C. sinensis metacercariae, were used in experimental chemotherapy. All the drugs used were administered intragastrically 42-44 d after infection. (1) Sixty infected rats were randomly divided into 11 groups (4-5 rats per group) and the following drug dose-schedules were applied, i.e. under the same total dose tribendimidine or praziquantel was given at a single dose of 150 mg/kg, or given at smaller divided doses of 75 mg/kg (qd for 2 d), 50 mg/kg (qd for 3 d), 25 mg/kg (tid for 2 d); artesunate or artemether was given at a single dose of 75 mg/kg, or given a half dose of 37.5 mg/kg daily for 2 days. (2) Eighty-seven infected rats were randomly divided into 15 groups (4-6 rats per group) for combined treatment with the following drug administration regimens, i.e. artesunate or artemether 30 mg/kg plus praziquantel 150 mg/kg or tribendimidine 50 mg/kg and 75 mg/kg, respectively; tribendimidine 50 mg/kg plus praziquantel 150 mg/kg; tribendimidine 75 mg/kg plus praziquantel 187.5 mg/kg. A single dose of each drug mentioned above was also involved. Untreated C. sinensis-infected rats served as control. Rats were killed 14 days post-treatment, worms recovered from the bile duct and the liver tissue, mean worm burden reduction calculated and mean worm burden compared between the groups using non-parametric method (Mann-Whitney test). RESULTS: Rats infected with C. sinensis and treated at a single 150 mg/kg dose of either tribendimidine or praziquantel resulted in a worm reduction of 57.2% and 63.8%, respectively. Whilst administration of tribendimidine at smaller but multiple doses given within 2-3 days at the same total dosage resulted in a slightly higher worm reduction (77.1%-79.4%), the opposite trend was observed for praziquantel (50.6%-54.2%). However, for both tribendimidine and praziquantel, the difference of mean worm burden lacked statistical significance between single and multiple doses. Infected rats administered either artesunate or artemether at a single dose of 75 mg/kg or a daily dose of 37.5 mg/kg for 2 days, the worm reduction was 100% and 90.4%-98.5%, respectively. Combined treatment with low doses of tribendimidine (50 mg/kg or 75 mg/kg) plus praziquantel (150 mg/kg or 187.5 mg/kg) resulted in a worm reduction of 74.9%-100%, which were higher than those of 26.9%-79.6% obtained from a single dose of each drug used. High worm reduction of 74.4%-97.9% was also observed when administering a low dose of artesunate or artemether (30 mg/kg) plus a low dose of tribendimidine (50 mg/kg or 75 mg/kg) or praziquantel (150 mg/kg). Mean worm reduction of 24.8%-79.6% were seen when drugs used at single doses. CONCLUSION: The investigation confirmed that tribendimidine, artesunate, artemether-and praziquantel are all efficacious against C. sinensis, and that drug combination acts synergistically.

Comparison of mitochondrial cytochrome oxidase 1 DNA sequences from Necator americanus hookworms maintained for 100 generations in golden hamsters (Mesocricetus auratus) and hookworms from natural human infections.

The human hookworm Necator americanus was maintained through one hundred generations in the golden hamsters. The strain is now routinely maintained in laboratory hamsters through serial passage, and is the laboratory strain of choice for vaccine studies. Comparison of the mitochondrial cytochrome oxidase 1 (cox-1) sequences was shown previously to be useful for comparing the genetic structure of populations of N. americanus in China. Cytochrome oxidase 1 genes were amplified by the polymerase chain reaction, and the sequences compared to those of N. americanus recovered from infected humans from several regions in China. Sequence comparison revealed little difference between the laboratory strain and the field isolates at the cox-1 locus, but also indicated that the laboratory strain is represented by a single cox-1 haplotype. These results suggest that the laboratory strain of N. americanus has undergone a severe genetic bottleneck, and that the genetic diversity in other genes, including potential vaccine antigens, could be similarly limited.