Morphological variation between isolates of the nematode Haemonchus contortus from sheep and goat populations in Malaysia and Yemen.

Haemonchus contortus is a highly pathogenic nematode parasite of sheep and goats. This work was conducted to investigate the population and host variations of the parasitic nematode H. contortus of sheep and goats from Malaysia and Yemen. Eight morphological characters were investigated, namely the total body length, cervical papillae, right spicule, left spicule, right barb, left barb, gubernaculum and cuticular ridge (synlophe) pattern. Statistical analysis showed the presence of morphological variation between populations of H. contortus from Malaysia and Yemen, with minor variation in the synlophe pattern of these isolates. Isolates from each country were grouped together in the scatterplots with no host isolation. Body, cervical papillae and spicule lengths were the most important characters that distinguished between populations of the two countries. This variation between Malaysia and Yemen may be attributed to geographical isolation and the possible presence of a different isolate of this worm in each country.

Sensitivity of two in vitro assays for evaluating plant activity against the infective stage of Haemonchus contortus strains.

The sensitivity of larval paralysis assay (LPA) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide-formazan (MTT-formazan) assay was compared to evaluate the anthelmintic activity of plant extracts. In this study, the methanolic extract of Azadirachta indica (neem) was evaluated for its activity against the infective-stage larvae (L(3)) of susceptible and resistant Haemonchus contortus strains using the two aforementioned assays. In both in vitro assays, the same serial concentrations of the extract were used, and the median lethal concentrations were determined to compare the sensitivity of both assays. The results revealed a significant difference (P < 0.05) in the sensitivity of the LPA and the MTT-formazan assay. The MTT-formazan assay is more feasible for practical applications because it measured the L(3) mortality more accurately than LPA. This study may help find a suitable assay for investigating the anthelmintic activity of plant extracts against trichostrongylid nematodes.

In vitro ovicidal and larvicidal activity of methanolic leaf extract of Manihot esculenta (cassava) on susceptible and resistant strains of Trichostrongylus colubriformis.

This study aimed to represent the first report of the ovicidal and larvicidal activity of the methanolic leaf extract of Manihot esculenta (cassava) against eggs and larvae of susceptible and resistant strains of Trichostrongylus colubriformis. As well as, to determine the total tannin compounds, antioxidant activity and toxicity of the extract. The egg hatch test was used to evaluate ovicidal activity against unembryonated eggs, whereas larval feeding inhibition assay and MTT-formazan assay were used to evaluate larvicidal activity against first (L(1)) and infective (L(3)) larvae, respectively. The results showed no significant differences were detected between the sensitivities of susceptible and resistant strains of T. colubriformis to the extract. Eggs, L(1) and L(3) were significantly affected (P<0.001) compared with negative control, and L(1) were more sensitive than the eggs and L(3). The total tannin compounds were investigated using tannin quantification assay and determined by 254.44 TAE/mg. The antioxidant activity was evaluated using the DPPH radical scavenging assay and the median inhibition concentration (IC(50)) was determined by 2.638 mg/ml. Acute oral toxicity at dose of 5,000 mg/kg, and sub-chronic oral toxicity at 500 and 1,000 mg/kg of the extract were observed in male and female Sprague-Dawley (SD) rats. The acute oral toxicity revealed that the median lethal dose (LD(50)) of methanolic extract of cassava leaves on SD rats was greater than 5,000 mg/kg, whereas the sub-chronic oral toxicity did not show observed adverse effects at 500 and 1,000 mg/kg per day for 28 days. In conclusion, the methanolic extract of cassava leaves has direct ovicidal and larvicidal activity against T. colubriformis strains with a safety margin for animals, and it may be potentially utilized as a source of natural antioxidants.

Genetic variation of Haemonchus contortus (Trichostrongylidae) in sheep and goats from Malaysia and Yemen.

The large stomach worm, Haemonchus contortus, commonly known as "the barber's pole worm", is a blood-sucking nematode found in the abomasa of sheep and goats. This work is the first documentation on the ND4 sequences of H. contortus from sheep and goats in Malaysia and Yemen and the results provide a preliminary insight on the genetic differences of H. contortus found in the two countries. In general, this study showed a high degree of diversity and low population structure of this species within the same country in comparison with higher genetic structuring at a wider geographical scale. The results also showed that the majority of genetic variance was within H. contortus populations. The Malaysian sheep and goat populations investigated appeared to share the same isolate of H. contortus while different isolates may be found in Yemen which must be taken into account in the design of an effective control strategy. Analysis of the internal transcribed spacer-2 (ITS-2) confirmed that all samples investigated in this study belonged to H. contortus. However presence of other Haemonchus species parasitizing these two hosts can only be confirmed by further detailed studies.

In vitro activity of neem (Azadirachta indica) and cassava (Manihot esculenta) on three pre-parasitic stages of susceptible and resistant strains of Teladorsagia (Ostertagia) circumcincta.

Anthelmintic resistance of gastrointestinal nematodes is considered as one of the main limiting factors causing significant economic losses to the small ruminant industry. The anthelmintic properties of some plants are among the suggested alternative solutions to control these parasitic worms. The present study investigated the anthelmintic activity of neem (Azadirachta indica) and cassava (Manihot esculenta) leaf extracts against the susceptible and resistant strains of one of the most important nematodes in small ruminants, Teladorsagia (Ostertagia) circumcincta. Three different in vitro tests: egg hatch test, larval development assay, and larval paralysis assay were used to determine the efficiency of neem and cassava extracts on three pre-parasitic stages of T. circumcincta. The LC(50) was determined for the most potent extract in each plant as well as the phytochemical tests, total tannin quantification and cytotoxicity on peripheral blood mononuclear cells of goats. The results revealed a high anthelmintic activity of neem methanol extract (NME) and cassava methanol extract (CME) on both strains of T. circumcincta without significant differences between the strains. The first stage larvae were more sensitive with the lowest LC(50) at 7.15 mg/ml and 10.72 mg/ml for NME and CME, respectively, compared with 44.20mg/ml and 56.68 mg/ml on eggs and 24.91 mg/ml and 71.96 mg/ml on infective stage larvae.

The seroprevalence of bovine babesiosis in Malaysia.

One hundred sera of Malaysian cattle were used in this seroprevalence study for bovine babesiosis. All sera were obtained from the Serological Unit of the Veterinary Research Institute (VRI), Ipoh, Perak. The sera were tested using a Veterinary Medical Research & Development (VMRD) commercial Indirect Immunofluourescent Antibody Test (IFAT) kit. The results showed that 17.0% were found to be positive for Babesia bovis, 16.0% for Babesia bigemina, and 9.0% for both B. bovis and B. bigemina infections.

Efficacy of agnique (mmf) monomolecular surface film against immature stages of Anopheles arabiensis patton and Culex spp (diptera: culicidae) in Khartoum, Sudan.

The efficacy of the larvicidal and pupicidal agent (Agnique) MMF was evaluated against larvae of An. arabiensis and Culex (Diptera: Culicidae) under field conditions in Bahary Locality, Khartoum, Sudan. At an applied dosage of 0.25 ml/m2, MMF resulted in 89.4, 79.8 and 88.2% reductions in L3-L4 instars An. arabiensis and 63.5% in Culex larvae (all stages) 24 to 72 hours post-treatment. Pupae were completely eliminated (100%) within 24 hours posttreatment. The earlier instars (L1-L2) of An. arabiensis were more tolerant with a 62.5% reduction at 72 hours post-treatment compared to (L3-L4) instars and pupae. At 7-days post-treatment Agnique gave a 57.5% reduction in L1-L2 and 92.6% in L3-L4 instar larvae of An. arabiensis and 57.3% and 86.4% in Culex larvae and pupae, respectively. We conclude that Agnique can perform effectively against L3-L4 instars and pupae of An. arabiensis for only 1 week, and 3 to 4 days against L1-L2 instars of Culex spp.

Species composition of adult Anopheles populations and their breeding habitats in Hulu Perak district, Peninsular Malaysia.

Using the cow-baited trap (CBT) method, 1,845 Anopheles mosquitos, comprising 14 species, were caught in malaria-endemic area of Hulu Perak district, Peninsular Malaysia. The two dominant species were An. barbirostris (18.59%) and An. aconitus (18.86%). Anopheles maculatus, the main malaria vector, constituted 9.11% of the total number of mosquitos sampled. Three hundred and seventy-seven Anopheles larvae, comprising 8 species, were sampled using the North Carolina Biological Station dipper. Anopheles barbirostris larvae amounted to 64.69% of the total number of larvae; An. aconitus accounted for 10.65% of larvae. Seven habitats were identified as breeding places of Anopheles. Most species were found to breed in paddies, fishponds, and rivers. Other less popular habitats were temporary pools, mountain streams, and spring wells.

Composition and biting activity of Anopheles (Diptera: Culicidae) attracted to human bait in a malaria endemic village in peninsular Malaysia near the Thailand border.

Nine species of Anopheles mosquitoes were collected biting humans indoors and outdoors in a malaria endemic village in northern Peninsular Malaysia. Outdoor biting was higher than that observed indoors. Biting of An. maculatus was observed throughout the night. Peak indoor biting occurred at 2130 h while outdoor biting was higher after midnight. Outdoor biting of Anopheles barbirostris and An. sinensis was observed throughout the night with several peaks after the second half of the night. Outdoor biting activities of An. kochi and An. philippinensis were primarily active after dusk and steadily declined after 2130 h.

A study on some aspects of the epidemiology of malaria in an endemic district in northern Peninsular Malaysia near Thailand border.

A study on the distribution of malaria in Hulu Perak district, Peninsular Malaysia was carried out between January and December 1993. The study encompassed the distribution of malaria cases according to sex, age and profession. A total of 332 cases were recorded, with 182 cases occurring in males. The highest infection was observed in the above 15 years old age group. Forest workers (loggers, rattan collectors and forest product gatherers) were the group most exposed to the disease (32.8%), followed by both plantantion workers (32.2%) and aboriginal communities (32.2%). Army and police personnels (2.1%) were also infected. Plasmodium falciparum was the most common species of malaria in the area.

Helminthic infections of urban and rural schoolchildren in Penang Island, Malaysia: implications for control.

The intestinal parasites of schoolchildren from an urban and a rural area on Penang island, Malaysia were compared. Examination of stool samples for helminth eggs showed that helminths found were Trichuris, Ascaris and hookworms. The results indicate that there is no significant difference (p<0.05) between rural and urban schoolchildren as regards to the prevalence of the three species of helminths. An extensive control program targetted at schoolchildren to monitor the helminth problem on the island is suggested.

The distribution of common Anopheles mosquitoes in northwestern Peninsular Malaysia.

Using cow-baited net traps in the coastal and hilly areas of northern peninsular Malaysia, 21 species of Anopheles mosquitoes were found. The distribution of common Anopheles is presented. The composition of the anopheline mosquito fauna was more diversified in the coastal areas than in the hilly areas. The displacement of Anopheles sundaicus by Anopheles subpictus and the disappearance of Anopheles hackeri in the coastal area were noted.

Malaria and Anopheles mosquitos in Malaysia.

Until today, malaria is still one of the most important diseases in Malaysia. This is because Malaysia is located within the equatorial zone with high temperatures and humidities, usually important for the transmission of malaria. The number of malaria cases were estimated to be around 300,000 before the launching of the Malaria Eradication Program (MEP). The program was successful in reducing the numbers progressively during the 1967-1982 period. During the period 1980-1991, the highest number of malaria cases recorded for the country was 65,283 in 1989 (16,902 in Peninsular Malaysia, 47,545 in Sabah and 836 in Sarawak) whilst the lowest was 22,218 (10,069 in Peninsular Malaysia, 11,290 in Sabah and 859 in Sarawak) in 1983. In Malaysia, there are 434 species of mosquitos, representing 20 genera. Of these, 75 species are Anopheles that comprise of 2 subgenus, i.e. Anopheles and Cellia. Of the 75 species, only 9 have been reported as vectors: An. maculatus, An balabacensis, An. dirus, An. letifer An. campestris, An. sundaicus, An. donaldi, An. leucophyrus and An. flavirostris. The behavior, seasonal abundance, biting activities and breeding sites of these species are discussed.

Comparative trials using albendazole and mebendazole in the treatment of soil-transmitted helminths in schoolchildren on Penang, Malaysia.

Trials using albendazole and mebendazole, as single 400 mg dose treatments, against soil-transmitted helminths, were carried out in 7-9 and 10-12 years-old schoolchildren living in urban and rural environments in Penang, Malaysia. Both drugs were equally effective in treating trichuriasis and ascariasis in both age groups and environments. However, mebendazole is not so effective in the treatment for hookworms when compared to albendazole. It is suggested that albendazole should be considered the drug of choice for mass chemotherapy for Penang.

A report of Anopheles (Diptera: Culicidae) attracted to cow bait in a malaria endemic village in Peninsular Malaysia near the Thailand border.

Twelve species of Anopheles were collected by using cow-baited net trap in a malarial endemic village in northern Peninsular Malaysia. Anopheles maculatus which is the main malaria vector with its densities were related to drought. An. aconitus, An. kochi and An. philippinensis were less susceptible to P. falciparum and P. vivax infection, and are not considered important in falciparum or vivax malaria transmission. Biting activities of An. kochi and An. vagus were primarily active after dusk and steadily declined after midnight. An. maculatus and An. aconitus showed biting activities throughout the night but An. maculatus showed two peaks of biting activity in the first half of the night.

Survey for drug-resistant trichostrongyle nematodes in ten commercial goat farms in west Malaysia.

The prevalence of drug-resistant parasites in goats in West Malaysia has rarely been reported. Ten commercial goat farms were surveyed for resistance to anthelminthics by measuring the reduction in faecal egg counts (FECs) after treatment with levamisole, pyrantel pamoate and fenbendazole. Resistance to fenbendazole was seen in most farms; there was no evidence of resistance to levamisole but some resistance to pyrantel pamoate was detected on one farm. The significance of the findings are discussed.

Resistance to benzimidazole anthelmintics by Haemonchus contortus in goats in peninsular Malaysia.

A previous study had suggested that local strains of goat trichostrongyles, comprising largely Haemonchus contortus, might have developed resistance to benzimidazole anthelmintics. A trial involving 18 goats was conducted to confirm this. There was a significant (P < 0.01) reduction in worm burdens in goats given levamisole, but this was not so for those animals given albendazole, fenbendazole, oxfendazole and mebendazole (P > 0.05).

The prevalence and intensity of soil-transmitted helminths in some rural villages in northern peninsular Malaysia.

The prevalence and intensity of soil-transmitted helminths in five rural villages in northern peninsular were investigated. Generally the prevalence and intensity of infection were low in the 0-10- and above 50-year-old age groups when compared with other age groups. The prevalence and intensity of infection in the five villages were quite similar, because of similar socio-economic status. The highest intensity was observed for Ascaris lumbricoides, followed by hookworms and Trichuris trichiura.

Effect of subclinical Eimeria species infections in tropical goats subsequently challenged with caprine Haemonchus contortus.

Fourteen goat kids of the local indigenous breed naturally infected with Eimeria species were divided into two equal groups. The first group was superinfected with 500,000 Eimeria species oocysts and the second group was treated with amprolium. Sixty days later both groups were infected with 5000 third-stage caprine Haemonchus contortus larvae. The goats experimentally superinfected with eimeria shed more H contortus eggs and gained weight more slowly.

An assessment of thiabendazole-resistant nematodes in some smallholder goat farms of Malaysia using the egg hatch assay method.

Faecal samples were collected from 48 randomly selected smallholder goat farms in northern Peninsular Malaysia. The nematode eggs extracted were tested for resistance to thiabendazole using the egg hatch assay technique. Thiabendazole resistance was found on 19% of farms tested.