Efficacy and toxicity of praziquantel in helminth-infected barbel (Barbus barbus L.).

This study evaluated efficacy and toxicity of the pyrazinoisoquinoline anthelmintic praziquantel (PZQ) in barbel infected with metacercariae of Diplostomum spathaceum and adult Pomphorhynchus laevis, and assessed antioxidant biomarkers and the lipid peroxidation response in juvenile barbel post-treatment. The estimated 96-hr LC50 of PZQ was 28.6 mg/L. For evaluation of efficacy, barbel naturally infected with D. spathaceum were exposed to a 10 and 20 mg/L PZQ 4-day bath treatment. Both concentrations were 100% effective against D. spathaceum and significantly (p < .01) affected the activity of catalase, superoxide dismutase, glutathione reductase and glutathione-S-transferase as well as levels of reduced glutathione in liver and muscle. The efficacy of orally administered PZQ was assessed in adult barbel naturally infected with P. laevis. Fish were administered 10, 30 and 50 mg/kg of body weight and examined via gut dissection after 6 days. The 50 mg/kg dose significantly decreased the intensity of infection. Praziquantel is a feasible bath treatment for barbel infected with D. spathaceum and has potential for oral treatment of broodfish infected with P. laevis.

Nanoemulsion from essential oil of Pterodon emarginatus (Fabaceae) shows in vitro efficacy against monogeneans of Colossoma macropomum (Pisces: Serrasalmidae).

Outbreaks of diseases pose a major threat to sustainable aquaculture development worldwide. Application of herbal products to combat parasitic diseases provides an alternative approach for sustainable aquaculture. This study investigated the in vitro antiparasitic effects of an oil-in-water nanoemulsion prepared using the essential oil from Pterodon emarginatus, against monogeneans infesting Colossoma macropomum. Gill arches from C. macropomum (47.6 ± 14.5 g and 13.5 ± 1.4 cm) that were naturally parasitized by Anacanthorus spathulatus, Notozothecium janauachensis and Mymarothecium boegeri were immersed in different dispersions of the P. emarginatus nanoemulsions (0, 50, 100, 200, 400 and 600 mg/L). The major compounds presented in the essential oil of P. emarginatus were ß-elemene, ß-caryophyllene and α-humulene. Characterization of these nanoemulsions showed that they have a small mean droplet size and low polydispersity index, which is concordant with stable systems. In this in vitro trial, the P. emarginatus nanoemulsion concentrations of 100, 200, 400 and 600 mg/L presented 100% helminthic efficacy against monogeneans of the gills of C. macropomum. The highest two concentrations used (400 and 600 mg/L) were seen to immobilize the parasites after only 15 min. Therefore, it would be worthwhile testing these concentrations in therapeutic baths against monogeneans of C. macropomum.

China's sustained drive to eliminate neglected tropical diseases.

Non-communicable diseases dominate the public health arena in China, yet neglected tropical diseases (NTDs) are still widespread and create a substantial burden. We review the geographical distribution, prevalence, and epidemic characteristics of NTDs identified in China caused by helminths, protozoa, bacteria, and viruses. Lymphatic filariasis was eliminated in 2007, but schistosomiasis still affects up to 5% of local village residents in some endemic counties with around 300 000 people infected. China harbours more than 90% of the world's burden of alveolar echinococcosis and food-borne zoonoses are emerging. In 2010, the overall prevalence of soil-transmitted helminth infections caused by Ascaris lumbricoides, Trichuris trichiura, and hookworm was 11·4%, with 6·8% of these infections caused by A lumbricoides. Corresponding figures for food-borne trematodiasis, echinococcosis, and cysticercosis are more than 5%. Dengue, leishmaniasis, leprosy, rabies, and trachoma exist in many areas and should not be overlooked. Transmission of vector-borne diseases can be interrupted; nevertheless, epidemics occur in remote areas, creating a challenge for surveillance and control. Rigorous surveillance, followed by immediate and integrated response packages tailored to specific social and ecological systems, is essential for progress towards the elimination of NTDs in China.

Cathepsin B proteases of flukes: the key to facilitating parasite control?

Cysteine proteases are important virulence factors for parasites. This review will focus on the cathepsin B proteases of trematodes (also known as flukes) which are abundant in juvenile and immature flukes. Recent research, primarily in Fasciola, using inhibitors, RNA interference (RNAi) and vaccination studies indicates that cathepsin Bs play a key role in the biology of trematodes. As these proteases are largely expressed by infective parasite stages, their inactivation by chemotherapy or vaccination will greatly reduce the damage wrought by flukes as they invade host tissues. This validates cathepsin Bs as key strategic targets for fluke control.

Zoonotic helminth infections with particular emphasis on fasciolosis and other trematodiases.

Zoonotic infections are among the most common on earth and are responsible for >60 per cent of all human infectious diseases. Some of the most important and well-known human zoonoses are caused by worm or helminth parasites, including species of nematodes (trichinellosis), cestodes (cysticercosis, echinococcosis) and trematodes (schistosomiasis). However, along with social, epidemiological and environmental changes, together with improvements in our ability to diagnose helminth infections, several neglected parasite species are now fast-becoming recognized as important zoonotic diseases of humans, e.g. anasakiasis, several fish-borne trematodiasis and fasciolosis. In the present review, we discuss the current disease status of these primary helminth zoonotic infections with particular emphasis on their diagnosis and control. Advances in molecular biology, proteomics and the release of helminth genome-sequencing project data are revolutionizing parasitology research. The use of these powerful experimental approaches, and their potential benefits to helminth biology are also discussed in relation to the future control of helminth infections of animals and humans.

Radioresistance of Anisakis simplex third-stage larvae and the possible role of superoxide dismutase.

The radioresistance of Anisakis simplex third-stage larvae and the possible role of sublethal radiation on superoxide dismutase (SOD) were investigated. Larvae were isolated from the viscera of the sea eel Anago anago; irradiated with 10, 100, 200, 500, or 1,000 Gy; and then given orally to rats. Worms were recovered at 16 hr postinoculation. Most larvae were found to have invaded the gastric wall, omentum, and abdominal cavity, suggesting that their viability and infectivity were not controlled by irradiation with the doses used. To determine the relationship between SOD activities in parasites and their radiosensitivities, the larvae of A. simplex and the metacercariae of Neodiplostomum seoulense (a radiosensitive control) were irradiated with 0, 30, 100, or 500 Gy, and parasite SOD levels were measured. In nonirradiated A. simplex larvae, the average SOD level was 38.9 U/mg, and this increased to 51.3 U/mg at 500 Gy. However, at all radiation doses applied, SOD activities of N. seoulense metacercariae were significantly (P < 0.05) lower than those of A. simplex larvae. Our results demonstrate that A. simplex third-stage larvae are radioresistant, and suggest that SOD plays a role in this radioresistance.

Treatment and control of the intestinal fluke, Skrjabinotrema ovis.

The small intestinal fluke, Skrjabinotrema ovis, is common among sheep in the Xinjiang region of western China. Up to 65,000 flukes per sheep were found during September when sheep were grazing summer pastures at high altitudes. Efficacy studies of some common flukicides revealed that oxyclosanide and triclabendazole were not effective in reducing the egg output of S. ovis, whereas closantel and praziquantel reduced egg counts by up to 98%. Praziquantel at 25 and 50 mg kg-1 reduced worm counts by 99%. Albendazole at 15 mg kg-1 reduced egg counts by 83% and worm counts by 91% but at lower dose rates it was ineffective.

[The effect of praziquantel on Trichobilharzia (Digenea, Schistosomatidae), a cause of swimmer's dermatitis in humans]. / Die Wirkung von Praziquantel auf Trichobilharzia (Digenea, Schistosomatidae), einen Verursacher von Badedermatitiden beim Menschen).

Cases of swimmer's itch caused by cercariae of the genus Trichobilharzia have spread during the last years in Southwestern Germany and increased in intensity. The only consequence was to forbid swimming because no effective strategies are known which would be ecologically or financially acceptable. In this examination we therefore tried, by means of medication of ducks, the possible final hosts, to kill the different stages of Trichobilharzia in patency and prepatency in order to interrupt the parasitic cycle. For this the effectiveness of praziquantel on the parasitic stages in the final host (preadults, adults, eggs or fully developed miracidia) was tested in experimentally infected dwarf mallards (Anas platyrhynchos, hemerot.) and mallards (Anas platyrhynchos platyrhynchos). During therapy of ducks with patent Trichobilharzia infection, onefold or twofold application of this drug (1 x 500 mg/duck, 1 x 300 mg/duck, 2 x 200 mg/duck) only prevented the releasing of eggs with hatchable miracidia for up to 24 h. Only a threefold application of 200 mg/duck in 24 h intervals led to a permanent reduction of detectable miracidia. Application of praziquantel in low doses (30 or 40 mg per duck and day) did not reduce the number of released miracidia. Medication with praziquantel led to a strong shift of adult worms located in the enteric veins of the ducks to the liver veins in a little as 3 h; examinations by scanning electron microscopy revealed changes in the worms' surface and damage of the tegument. During prepatency doses of 22.5 mg praziquantel per duck and day, given continuously for one week, were sufficient to completely stop the release of miracidia. In this low dosage, a special preparation of the bitter drug was voluntarily swallowed by the ducks, thus providing in principal a simple, cheap and ecologically sound method of controlling cercarial dermatitis.

Heterophyids: experimental chemotherapy and immunotherapy.

Heavy infections with the tiny flukes heterophyids can cause intestinal pain and mucous diarrhea, thus the study of praziquantel (Pzq) and the new drug cyclosporin A (CsA) as antiparasitic drugs were undertaken in this work, as well as the effect of matecercarial and adult antigens as immunizing agents. To assess the result of our work, the number and length of the recovered heterophyids were studied. Description of the surface by SEM was carried out for the groups: treated by cyclosporin A and immunized by adult heterophyid antigen (third fraction) which gave the highest percentage reduction.

[Experimental control study of fasciolopsiasis in Taiwan].

This study was conducted from March 1985 to September 1987 among the pupils of Chung-Ying Primary School of Hsia-Ying township in Tainan Country, Southern Taiwan. Health education revealed the preferred control method against Fasciolopsis infection in this study. The education method included lectures, demonstrations of parasites and home visits at regular intervals. The subjects included the staff and children of the school and all family members. At the same time, the children infected with Fasciolopsis were treated with praziquantel in June, 1986. Fecal material of the all primary school children of Hsia-Ying township was examined with the antiformin-ether concentration method. One year before control the positive rate of Fasciolopsis was 25.1%. One year after control in March 1986, it was decreased to 9.5%. Two and a half years after control in September 1987, it was farther brought down to 1.0%. The x2-test of positive rate showed statistically different. Health education with medication is recommended for the control of fasciolopsiasis.

Health education in control of fluke infections.

Human trematode infections are largely confined to the tropical and oriental countries. Especially schistosomiasis, clonorchiasis, paragonimiasis, heterophydiasis and fasciolopsiasis are great public health problems in certain countries. The control of clonorchiasis, paragonimiasis and intestinal fluke infections theoretically is very simple, as the infection is transmitted to man mostly by eating fish and crabs serving as intermediate hosts and harbouring metacercariae. It is different with schistosomiasis where, by contact with contaminated water, man gets infected with cercarial larvae penetrating the intact skin. Therefore, prophylactic measures are far more difficult to apply successfully. Thus, except in schistosomiasis, the most practical method of preventing human trematode infections is to avoid eating raw, freshly pickled or imperfectly cooked fresh-water fish, crayfish or crabs, etc. It is, however, exceedingly difficult to enforce such simple measures in face of century old traditions, to which relatively primitive populations cling with great tenacity. Therefore, in areas where the consumption of raw fish or crabs is customary, insistent and persistent educational propaganda stressing the importance of thoroughly cooking all fresh-water fish or crabs appears to be the most effective means of preventing such diseases. Such educational efforts should be directed primarily toward school children because they are less entrenched in their food habits. Thus, the educational process could involve various levels to successively change knowledge, attitudes, behaviour, habits and customs of their lives. However, this could better be accomplished by supporting health education by successful chemotherapy.