Biological control of nematode parasites of livestock in Fiji: screening of fresh dung of small ruminants for the presence of nematophagous fungi

Natural occurrence and distribution of entomopathogenic nematodes (Steinernematidae, Heterorhabditidae) in Viti Levu, Fiji Islands

In Fiji, little or no attention has been given to entomopathogenic nematodes (EPNs) in biocontrol programs due to the lack of awareness about their occurrence and distribution in Fiji. A survey of EPNs was conducted for the first time in Fiji Islands in 2012 and 2013, throughout the eight provinces in Viti Levu to determine the occurrence and distribution across different habitat in Viti Levu. The soil samples from various habitats were collected and assayed for the presence of EPN using Galleria mellonella as baits. EPNs were recovered from five out of seven provinces with 35 positive sites (7.3%) out of 478 sites sampled. The only EPN genera encountered was Heterorhabditis. Steinernema was not isolated from any of the samples. Characterization of isolates was done by using morphometric and molecular examinations and isolates were identified as Heterorhabditis indica. H. indica isolates were primarily recovered from leeward side of the Viti Levu Island along the coastline and riversides, being more prevalent in lighter soil with pH > 6. Further, this study found significant association between habitat type, soil type, soil pH, average annual rainfall and EPN occurrence. This is the first record of naturally occurring EPNs in Fiji. The found nematodes will serve as the basis for efficacy screening with the ultimate aim of delivering effective, more sustainable and environmentally safe control for agricultural pests in Fiji.

In Fiji, little or no attention has been given to entomopathogenic nematodes (EPNs) in biocontrol programs due to the lack of awareness about their occurrence and distribution in Fiji. A survey of EPNs was conducted for the first time in Fiji Islands in 2012 and 2013, throughout the eight provinces in Viti Levu to determine the occurrence and distribution across different habitat in Viti Levu. The soil samples from various habitats were collected and assayed for the presence of EPN using Galleria mellonella as baits. EPNs were recovered from five out of seven provinces with 35 positive sites (7.3%) out of 478 sites sampled. The only EPN genera encountered was Heterorhabditis. Steinernema was not isolated from any of the samples. Characterization of isolates was done by using morphometric and molecular examinations and isolates were identified as Heterorhabditis indica. H. indica isolates were primarily recovered from leeward side of the Viti Levu Island along the coastline and riversides, being more prevalent in lighter soil with pH > 6. Further, this study found significant association between habitat type, soil type, soil pH, average annual rainfall and EPN occurrence. This is the first record of naturally occurring EPNs in Fiji. The found nematodes will serve as the basis for efficacy screening with the ultimate aim of delivering effective, more sustainable and environmentally safe control for agricultural pests in Fiji.

Isolation, identification and characterization of the nematophagous fungus Arthrobotrys (Monacrosporium) sinense from China

With the development of anthelmintic resistance of parastic nematodes, it is necessary to isolate and study nematophagous fungi to screen out the native isolates for their potential in the biocontrol of domestic animal nematodosis. This study aimed to isolate the Arthrobotrys sinense (Monacrosporium sinense) of nematophagous fungus, to characterize representative molecular isolates using scanning electron microscope (SEM), and to determine the effect of the temperature and pH values on radial growth of the isolate. Five isolates were isolated from 1532 samples of different types, and their occurrence frequencies were 0.32% of the total samples. They were identified as A. sinense by means of morphology and the sequence of the 5.8S, 18S, and 28S rDNA, as well as internal transcribed spacers 1 and 2. The isolate NBS003 could grow from 11°C to 35°C and had optimal growth at 30°C. The isolate could grow at pH 4 to 11, and its optimal value was obtained at pH 9. SEM results showed that 6 h after their addition, the second stage larvae (L2) and the third stage infective larvae (L3) of Haemonchus contortus were captured. L2 and L3 were penetrated by the fungus at 18 and 24 h post-capture, respectively. L2 and L3 were completely digested at 84 and 90 h post-capture, respectively. The NBS003 of the A. sinense should have a certain potential to be used for capturing the free-living stage of nematodes in sheep.

Isolation of Ovicidal Fungi from Fecal Samples of Captive Animals Maintained in a Zoological Park

There are certain saprophytic fungi in the soil able to develop an antagonistic effect against eggs of parasites. Some of these fungal species are ingested by animals during grazing, and survive in their feces after passing through the digestive tract. To identify and isolate ovicidal fungi in the feces of wild captive animals, a total of 60 fecal samples were taken from different wild animals kept captive in the Marcelle Natureza Zoological Park (Lugo, Spain). After the serial culture of the feces onto Petri dishes with different media, their parasicitide activity was assayed against eggs of trematodes (Calicophoron daubneyi) and ascarids (Parascaris equorum). Seven fungal genera were identified in the feces. Isolates from Fusarium, Lecanicillium, Mucor, Trichoderma, and Verticillium showed an ovicidal effect classified as type 3, because of their ability to adhere to the eggshell, penetrate, and damage permanently the inner embryo. Penicillium and Gliocladium developed a type 1 effect (hyphae attach to the eggshell but morphological damage was not provoked). These results provide very interesting and useful information about fungi susceptible for being used in biological control procedures against parasites.

A review of domestic animal diseases within the Pacific Islands region

The Pacific Island countries and territories (PICTs) are reported to be free of the most serious infectious livestock diseases which are prevalent in other parts of the globe, such as Highly Pathogenic Avian Influenza, Foot and Mouth Disease or Rabies. Yet there is a lack of scientifically based evidence to confirm this animal health status. This paper reviews what has been published on diseases of domestic animals in the Pacific Islands region with a particular focus on data from the last 20 years (1992-2012). Relevant published papers were identified by a computerized literature search of two electronic databases (PubMed and Web of Knowledge). The latest reports on the animal health situation submitted by the PICTs to the World Organisation for Animal Health (OIE) were accessed on the World Animal Health Information Database (WAHID) interface and included in this review. Additionally, paper searches of resources were undertaken at the library of the Secretariat of the Pacific Community (SPC) in Fiji to retrieve any relevant grey literature for this review. The study eligibility criteria included qualitative or quantitative information on any disease (bacterial, viral, parasitic and other health disorders) affecting domestic terrestrial animals (mammals, reptiles, birds and bees) in any of the 22 PICTs members of the SPC. A total of 158 eligible references were retrieved of which only 77 (48.7%) were published since 1992 and analysed in more details. One hundred and one diseases and pathogens were reported on for bee, bird, carabao, cat, cattle, crocodile, deer, dog, donkey, goat, horse, pig, pigeon, poultry and sheep in the Oceania region and in 17 PICTs in particular. The paper gives information about known animal diseases, their reported prevalence and diseases not reported within the Pacific Islands region. The study found retrieved literature on animal diseases in PICTs was scarce and no longer up to date. There is a need to improve the published knowledge on the current animal disease status in the region.

Isolation and characterization of the nematophagous fungus Arthrobotrys conoides

The spread of organic farming and the development of resistance to anthelmintics by parasites, especially in small ruminants, have necessitated the search for alternative methods of nematode control. Biological control using nematophagous fungi is one option; however, few studies have been conducted with native strains. The present study was divided into two phases. In the first phase, we aimed to isolate, identify, and assess the in vitro predatory activity of nematophagous fungi that had been isolated on Trichostrongylidae third-instar larvae. In the second phase, the isolate with superior predatory activity in vitro was molecularly characterized, and its morphological plasticity was observed using scanning electron microscopy (SEM) on Haemonchus third-instar larvae. Of the 56 soil samples from different regions of Paraná State, Brazil, 57 fungal strains were recovered, of which four exhibited predatory activity. Two pure isolates were obtained: the CED and LIN strains. After demonstrating 96.35 % predatory activity for the CED strain, this strain was selected and characterized using molecular criteria by sequencing the rDNA internal transcribed spacer and was identified as Arthrobotrys conoides (GenBank ID: JN191309). Morphological patterns in this strain during the interaction between the fungus and the nematode were revealed by SEM, in which two extensions of the infection bulb that was used to pierce the nematode's cuticle were clearly visible.

The ecology of nematode-trapping hyphomycetes in cattle dung from three plateau pastures

This paper investigated the influence of season and altitude on the occurrence of nematode-trapping fungi in cattle faeces. Six hundred and sixty samples of cattle faeces deposited on three plateau pastures with different altitudes in the west of Yunnan Province, China, were examined in 2004. A total of 17 species of nematode-trapping hyphomycetes were isolated from these samples. The predominant species from all three plateau pastures were Arthrobotrys oligospora, A. musiformis, Monacrosporium ellipsosporum, and M. thaumasium. Species with adhesive networks were the most frequently isolated. Overall, species diversity index was negatively correlated with altitude and was different among seasons within the same site. Levels of diversity were highest in the summer, followed by autumn, spring, and winter. The conidia of the hyphomycetes isolated here germinated normally on medium containing cattle faeces, with species developing adhesive networks having the highest rate of germination. However, the rate of conidial trap (CT) formation was lower in species with adhesive networks than those in other species.

Viabilidade de formulação peletizada do fungo nematófago Monacrosporium sinense, no controle biológico de nematóides parasitos gastrintestinais de bezerros

A viabilidade de uma formulação do fungo Monacrosporium sinense foi avaliada no controle de nematóides parasitos gastrintestinais de bovinos. Dois grupos de 10 bezerros cada um, mestiços Holandês x Zebu, de seis a nove meses de idade, foram colocados em pastagem de Brachiaria brizantha. Em um dos grupos, cada animal recebeu 20g de péletes em matriz de alginato de sódio, contendo massa miceliana do fungo M. sinense via oral, duas vezes por semana, durante seis meses, com início no mês de outubro; no outro grupo, controle, os bezerros não receberam esse tratamento. As contagens de ovos por grama de fezes (OPG) e de larvas infectantes por kg de matéria seca foram maiores (P<0,05) no grupo-controle, e a diferença entre o OPG dos dois grupos, no final do experimento, foi de 79%. A viabilidade dos péletes em germinar e a atividade predatória do fungo após o encapsulamento foram avaliadas in vitro. A porcentagem de péletes com cultivo positivo para o fungo variou entre 90 e 100%, e o percentual de redução de larvas infectantes in vitro variou entre 90,6 e 100%. A aplicação de péletes de M. sinense na dosagem e periodicidade usadas são eficazes no biocontrole de nematóides parasitos gastrintestinais de bovinos.

Anthelmintic resistance: The state of play revisited

Helminthosis is one of the major constraints in the successful wool and mutton industry throughout the world. Anthelmintic Resistance (AR) is said to have been established when previously effective drug ceases to kill exposed parasitic population at the therapeutically recommended dosages. Anthelmintic resistance is almost cosmopolitan in distribution and it has been reported in almost all species of domestic animals and even in some parasites of human beings. Some of the most important species of parasites of small ruminants in which AR has been reported include: Haemonchus spp., Trichostrongylus spp. Teladorsagia spp., Cooperia spp. Nematodirus spp., and Oesophagostomum spp. All the major groups of anthelmintics have been reported for development of variable degrees of resistance in different species of gastrointestinal nematodes. This paper describes the global scenario of prevalence and methods used for detection of AR in small ruminants. Different mechanisms and contributory factors for the development of AR are discussed. Various options and alternate strategies for the control and/or delay in the onset of AR are suggested in the light of available information.

Biological control of nematode parasites in sheep1

In a world in which sheep producers are facing increasing problems due to the rapid spread of anthelmintic resistance, the battle against gastrointestinal parasitic nematodes is a difficult one. One of the potential new tools for integrated control strategies is biological control by means of the nematode-destroying microfungus Duddingtonia flagrans. This fungus forms sticky traps that catch developing larval stages of parasitic nematodes in the fecal environment. When resting spores (chlamydospores) of this fungus are fed daily to grazing animals for a period of time, the pasture infectivity and thus, the worm burden of grazing animals are lowered, especially in young lambs. Research has been conducted throughout the world covering many different climates and management systems. An Australian parasite model showed that if the fungus performs efficiently (> or =90% reduction in worm burden) for 2 or 3 mo, it should contribute significantly to a reduction in the number of dead lambs otherwise occurring when managed only by anthelmintic treatment and grazing management. Feeding or field trials have clearly demonstrated that dosing with a few hundred thousand spores per kilogram of live BW not only reduced the number of infective larvae but also increased the BW of the lambs compared with controls not given fungus. Initial Australian work with feeding spores by means of a block formulation or a slow-release device has shown some promise, but further work is needed to fully develop these delivery systems. In tropical Malaysia, small paddock trials and field studies resulted in significant improvements, in terms of lower worm burdens and increased live BW, when feeding half a million spores daily to grazing lambs. Additional benefits have been observed when the fungus is employed in combination with a fast rotational grazing system. Research has also demonstrated that spores can be delivered in slightly moist feed block material, but only if such blocks are consumed rapidly, because of their very short shelf life. In the northern, temperate Danish climate it has been demonstrated that daily feeding of half a million spores per kilogram of live BW can lead to significant production benefits, with increased live BW gain in fungus-exposed animals. Biological control of parasitic nematodes in sheep seems to hold promise for the future, but to be able to assist producers, the optimal delivery system needs to be refined and further developed. In addition, more work will be needed to define the best use of this technology in different geographic regions.

The predatory capability of Arthrobotrys cladodes var. macroides in the control of Haemonchus contortus infective larvae

One hundred compost samples were examined for the presence of nematophagous fungi on the sheep farms of Mazanderan, province, Iran. Arthrobotrys cladodes var. macroides (IRAN 677C=CBS 143565) was isolated from 3% of the samples examined. Nematophagous activity of this fungus which was shown for the first time in this study, revealed the addition of 1000, 8000, 20000 and 100000 conidia per gram of feces of sheep reduced significantly (P<0.001) the number of Haemonchus contortus infective larvae in the feces by 41.71%, 63, 27%, 73.49% and 94.96%, respectively. These results show that A. cladodes var. macroides is a promising candidate for biological control of H. contortus.

Improvement on genetic transformation in the nematode-trapping fungus Arthrobotrys oligospora and its quantification on dung samples

An improved DNA-mediated transformation system for nematode-trapping fungus Arthrobotrys oligospora based on hygromycin B resistance was developed. The transformation frequency varied between 34 and 175 transformants per microg linearized DNA and 93% of the transformants were stable for drug resistance when tested 100 randomly selected transformants. More than 2000 transformants were obtained by transformation of the fungus with pBChygro in the presence of HindIII and among them, one, YMF1.00110, which lost its ability of forming predacious structure, was isolated. Southern analysis showed that the plasmid DNA had integrated into the genome of all tested transformants (including YMF 1.00110) except one. The transformant tagged with hph gene could be re-isolated and quantified from dung samples based on the resistance of hygromycin B. All the results suggested that the method of restriction enzyme mediated integration (REMI) should facilitate not only the insertional mutagenesis for tagging and analysis genes of interest but also the ecological investigation of tagged fungi in a given environment.