Summary
Human schistosomiasis is one of the most important parasitic diseases. It is reported to be endemic in 77 countries in tropical and subtropical regions, leading to infection of about 250 million individuals worldwide. The economic and health effects of schistosomiasis are considerable.
Treatment of schistosomiasis worldwide relies very heavily on PZQ, but the development of drug resistance has drawn the attention of many researchers to alternative drugs of plant origin which may be helpful in the treatment of schistosomiasis. Garlic is one of these plants. It is known as an antiparasitic agent and this activity has been attributed to allicin, the main constituent of garlic.
The objective of the current study was to evaluate the potential therapeutic and/or prophylactic effects of allicin on S. mansoni.
(1) Effect of allicin on S. mansoni in vitro:
Different concentrations of allicin (5, 10, 25, 50, 100 and 200 µg/ml) were incubated with immature and adult S. mansoni worms in culture plates for 96 hrs. They were monitored every 24 hrs to evaluate their motor activity and mortality rate by light microscopy. Scanning electron microscopy examination was used for ultrastuctural analysis of the effect of allicin against worms after 72 hrs.
(2) Effect of allicin on murine schistosomiasis:
Mice infected with S. mansoni cercariae were classified as following (each group had 10 mice):
Group 1: Infected non-treated (control).
Group 2: Infected and treated with allicin (8mg/ Kg by intravenous route) 24 hrs before infection, the same day of infection and 24 hrs post infection (prophylactic group).
Group 3: Infected and treated with allicin (8mg/ Kg by intravenous route) one week post infection for 3 days (therapeutic effect on schistosomules).
Group 4: Infected and treated with allicin (8mg/ Kg by intravenous route) 6 weeks post infection for 4 days (therapeutic effect on adult worms).
All mice were sacrificed 54 days post infection.
The effect of allicin on S. mansoni infected mice was evaluated by parasitological investigations including worm burden, oogram pattern and tissue egg load (intestine and liver).
Results revealed that:
(1) Effect of allicin on S. mansoni in vitro:
In vitro incubation of S. mansoni immature worms with allicin, at concentrations of 50,100 and 200 µg/ml, showed a statistically high significant difference in comparison with control non-treated group. Only 72 hrs were needed to have complete death of all worms at a concentration of 200 µg/ml of allicin, while at 100 µl/ml concentration required 96 hrs to kill 50% of the worms. At 50 µl/ml concentration, there was no death until the end of the experiment, but all worms showed sluggish movement. No effect was noticed at allicin concentrations of 25, 10 and 5 µg/ml until the end of the experiment. SEM of immature worms after 72 hrs showed oedema of the oral sucker, shrunken ventral sucker and vesicles formation.
In vitro incubation of S. mansoni adult worms with allicin, at concentration of 100 µg/ml and 200 µg/ml, showed a statistically high significant difference in comparison with control non-treated group. Only 72 hrs were needed to have complete death of all worms at a concentration of 200 µg/ml of allicin, while at 100 µl/ml concentration required 96 hrs to achieve the same effect. No lethal effect was noticed at allicin concentrations of 50, 25, 10 and 5 µg/ml until the end of the experiment. SEM of adult worms after 72 hrs showed oedema of the oral sucker, extensive tegumental destruction with loss of tubercles and spines, vesicles formation, multiple erosions and peeling.
(2) Effect of allicin on murine schistosomiasis:
1-Worm burden (54 days post infection):
There was a slight decrease in the mean number of male and female worms observed in all treated groups which was non-significant statistically (p value >0.05). However, there was an increase in the mean number of couple worms and total worm burden observed in all treated groups which was non-significant statistically (p value >0.05).
2- Oogram pattern (54 days post infection):
Allicin treated group 6 weeks post infection had high significant increase in dead egg percentage and high significant decrease in immature and mature egg percentages (P value |
