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PubMed1994

Dispersion statistics and sample size estimates for house fly (Diptera: Muscidae) larvae and Macrocheles muscaedomesticae (Acari: Macrochelidae) in poultry manure.

The precision of the density estimate for a given population depends upon the population's density and degree of clumping and upon sampling characteristics, such as the number and surface area of the quadrats. The parameters k of the negative binomial distribution and b of Taylor's power law (s2 = a mean b) were determined for third instars of the muscaedomesticae (Scopoli), which were sampled by random quadrats at two shallow-pit, caged-layer poultry houses. Most calculated values of k were < 1, but agreement with the negative binomial distribution was found only in 4, 18, and 14 of the 27 weekly samples for house fly larvae, female mites, and male mites, respectively. Taylor's power law provided the best fit for the distribution (P < 0.01 for all regression coefficients) with s2 = 9.08 mean 1.83 (r2 = 0.97) for third-instar house flies and s2 = 4.65 mean 1.76 (r2 = 0.97) for both sexes of M. muscaedomesticae. Two ecological processes, social clustering and environmental heterogeneity, were hypothesized as the mechanisms determining aggregation of house fly larvae and the macrochelid mites. Regardless of the biological model influencing their distributions, Taylor's power law provided a reliable index for measuring their degree of aggregation. Reliability defined by the coefficient of variability and Taylor's regression coefficients was used to calculate optimum sample size-density estimates for each species with coefficients of variability of 10, 15, 20, and 25%.

Animals↗

PubMed1994

[Ectoparasites of animals: methods of ecological, biological, genetic and mechanical control].

The use of insecticides is still the basic procedure for controlling most ectoparasites, but various methods are being developed to act in addition to, or in synergy with these products, so as to enhance the efficacy and reduce the adverse effects of insecticides, by contributing to ecologically acceptable strategies. These methods are classified as ecological control (modification of the environment of the parasite), biological control (predation, parasitism, action of pathogens, etc.), genetic control (release of sterile males, hybridisation, genetic manipulations) and mechanical control (insect traps, use of repellents). The application of such methods depends on the biological and ecological characteristics of the ectoparasite, and they may act directly or indirectly, affecting mortality and/or reproduction. The authors review the principal methods applicable to major groups of ectoparasites of veterinary interest. Non-chemical methods are the subject of wide-ranging and promising research, particularly in view of recent developments in biotechnology.

Animals↗

PubMedDate not supplied

Biological control program against simuliids in the State of São Paulo, Brazil.

In Brazil, the use of biological vector-control methods has been largely confined to experimental research, with little or no application of such techniques by public institutions responsible for implementing control programs. The notable exceptions have been the black fly control program carried out by the Health Secretariat in the State of São Paulo. Since the 1980s, São Paulo's "Superintendência de Controle de Endemias" has been conducting studies on the viability of using Bacillus thuringiensis (H-14) for simuliid control, and the results have been so encouraging that the agency has now incorporated this method into its Simuliid Control Program.

Animals↗

PubMedDate not supplied

[Bacillus thuringiensis: biological characteristics and production perspectives].

In this paper the potential activity of Bacillus thuringiensis as insecticide is reviewed. It is presented recent knowledges of its metabolism, production system and the rinetic constants already reported finally the possibilities for production in batches or continuous culture is discussed in order to improve the productivity and economical aspects.

Animals↗

PubMed2006

The prey-dependent consumption two-prey one-predator models with stage structure for the predator and impulsive effects.

In this paper, we consider the prey-dependent consumption two-prey one-predator models with stage structure for the predator and impulsive effects. By applying the Floquet theory of linear periodic impulsive equation, we show that there exists a globally asymptotically stable pest-eradication periodic solution when the impulsive period is less than some critical value, that is, the pest population can be eradicated totally. But from the point of ecological balance and saving resources, we only need to control the pest population under the economic threshold level instead of eradicating it totally, and thus, we further prove that the system is uniformly permanent if the impulsive period is larger than some critical value, and meanwhile we also give the conditions for the extinction of one of the two preys and permanence of the remaining species. Thus, we can use the stability of the positive periodic solution and its period to control insect pests at acceptably low levels. Considering population communities always are imbedded in periodically varying environments, and the parameters in ecosystem models may oscillate simultaneously with the periodically varying environments, we add a forcing term into the prey population's intrinsic growth rate. The resulting bifurcation diagrams show that with the varying of parameters, the system experiences process of cycles, periodic windows, periodic-doubling cascade, symmetry breaking bifurcation as well as chaos.

Animals↗

PubMed1996

[Construction of shuttle vector containing delta-endotoxin gene of Bacillus thuringiensis].

The Bacillus thuringiensis toxin gene CryIA(c) was inserted into the shuttle vector pBE-2 to construct pAMY for expressing the B.t. gene in both Gram-negative and -positive bacterial systems. pAMY was introduced into wild type Bacillus cereus, B.brevis and B.subtilis by electroporation. Transformants containing delta-endotoxin gene produced proteins reacted with B.t. crystal protein antibody. Upon biological toxicity tests, the transformants gave a mortality of 100% against Ostrinia furnacilis, 58.8% against Heliothis armigera and 100% against Heliothis assulta. The ability of promoting plant growth of the original strains is retained.

Bacillus cereus↗

PubMed1999

Transformation of Candida oleophila and survival of a transformant on orange fruit under field conditions.

Histidine auxotrophs of wild-type strain I-182 of Candida oleophila, produced using ethyl methanesulfonate, were transformed with plasmids containing the HIS3, HIS4 and HIS5 genes of Saccharomyces cerevisiae. Histidine auxotrophy was complemented by the HIS5 gene of S. cerevisiae. Stability of the transformants under non-selective conditions and DNA gel-blot analysis suggested that the transforming DNA had integrated into the C. oleophila genome. There were no detectable physiological differences between the wild-type and the transformants. The biological control ability of C. oleophila was not affected by the transformation. A genetically marked transformant (with a beta-glucuronidase gene) colonized wounds on oranges, and its population increased under field conditions. The identity of the genetically marked transformant was established by PCR-amplification of a portion of the beta-glucuronidase gene.

2-Aminoadipic Acid↗

PubMed2005

Evaluation of upstream point treatment in flowing water ditches by Aquabac (Bacillus thuringiensis var. israelensis) against Culex quinquefasciatus.

The effectiveness of the upstream point treatment by AQUABAC Biolarvicide (Bacillus thuringiensis var. israelensis, Biological Larvicide Aqueous Suspension) against Culex quinquefasciatus Say in slow-flowing water ditches has been evaluated in St. Augustine Beach, St. Johns County, FL. The upstream point treatment by AQUABAC (liquid) at 0.5 liter/acre provided significant levels of larval control of Cx. quinquefasciatus for all sections of the downstream for 9 days. The upstream point treatment method by larvicides may have potential for use, minimize environmental impacts, and reduce cost and labor in mosquito-control operation for slow-flowing water ditches.

Animals↗

PubMed2005

Assessment of cone-damaging insects in a Swedish spruce seed orchard and the efficacy of large-scale application of Bacillus thuringiensis variety aizawai x kurstaki against lepidopterans.

In a 2-yr study, we investigated the efficacy of large-scale application of the biological insecticide Bacillus thuringiensis variety aizawai x kurstaki (Btk) in a Swedish spruce, Picea abies L. (Karst.), seed orchard for controlling damage caused by four lepidopteran species: Dioryctria abietella Den et. Schiff. (Pyralidae), Eupithecia abietaria Götze, E. analoga Djakonov (Geometridae), and Cydia strobilella (L.) (Tortricidae). The frequencies of these species, and Strobilomyia anthracina Czerny (Diptera: Anthomyiidae), were regularly monitored throughout the vegetative growth season to map their temporal distribution patterns and to quantify occurrences of species that may have been present in the cones at some stage during the season but migrated before the final sampling. This investigation revealed that E. abietaria occurred in similar numbers to D. abietella and has probably been overlooked as a potentially serious pest in spruce seed orchards in Sweden. To determine the number, timing, and rate of Btk required to control the lepidopterans, spraying was conducted at different phases of flowering and cone development, and three rates of Btk were applied. The Btk treatment reduced cone damage caused by D. abietella and Eupithecia spp. by one-half in 2002, a year with an intermediate number of cones, but the effect was weaker in 2003, when the cone crop was low. Damage caused by C. strobilella was not affected by the treatment. The different rates of Btk application did not affect the results, and repeated spraying seemed to be effective during 2002 but not in 2003.

Animals↗

PubMed2003

Lessons learned from the emergence of a new Trypanosoma brucei rhodesiense sleeping sickness focus in Uganda.

During the latter months of 1998, cases of sleeping sickness caused by Trypanosoma brucei rhodesiense presented in Soroti district, eastern Uganda, a region which had not previously experienced cases of the disease. Cattle are the main reservoir for T b rhodesiense, by contrast with sleeping sickness caused by Trypanosoma brucei gambiense in west Africa where there appears to be no epidemiologically significant animal reservoir. Several factors have been identified that interacted to produce ideal conditions for the establishment of a new disease focus. After a period of civil unrest, Soroti, which is within the tsetse belt, was repopulated by people and later, cattle. Both the cattle restocking and the subsequent trade in these cattle at a local cattle market had a role in the appearance of the disease. Recently, molecular biology techniques have become available for the detection and genotype identification of T b rhodesiense and thus it is now possible to distinguish human infective and non-infective trypanosomes in cattle. In light of these advances in identification and in both field and epidemiological techniques, successful disease control management has become an achievable goal and will require the collaboration and expertise of clinicians, veterinarians, epidemiologists and laboratory scientists.

Animals↗

PubMed1997

Nematode-trapping fungi in biological control of Dictyocaulus viviparus.

Larvae of the cattle lungworm Dictyocaulus viviparus were cultured in experimental units of 200 g cattle faeces placed in semi-transparent trays in the laboratory. In each of 4 experimental series using this experimental unit, chlamydospores (chl) of the nematode-trapping fungus Duddingtonia flagrans were admixed to half of the faecal cultures in a concentration of 50.000 chl/g. In all 4 series there was a significant reduction in the development and subsequent release of infective lungworm larvae from faecal cultures containing chlamydospores. The average reduction in larval release, caused by fungal spores, was 86%.

Animals↗

PubMed2006

Bacillus thuringiensis and Bacillus sphaericus biopesticides production.

The long residual action and toxicity of the chemical insecticides have brought about serious environmental problems such as the emergence and spread of insecticide resistance in many species of vectors, mammalian toxicity, and accumulation of pesticide residues in the food chain. All these problems have highlighted the need for alternative biological control agents. Entomo-pathogenic Bacillus thuringiensis (Bt) and Bacillus sphaericus (Bs) are two safe biological control agents. They have attracted considerable interest as possible replacements for the chemical insecticides. Although microbial insecticides based on Bt and Bs are available for use, their high cost makes large-scale application impracticable in developing countries. This review focuses on the economic production of these two microorganisms by submerged fermentation and solid state fermentation using agro-industrial by-products and other wastes.

Animals↗

PubMed2001

Chrysosporium tropicum efficacy against Anopheles stephensi larvae in the laboratory.

The keratinophilic soil fungus Chrysosporium tropicum was evaluated as a biological control agent against Anopheles stephensi larvae in the laboratory. Culture filtrates of C. tropicum were found to be toxic to An. stephensi larvae at various concentrations. The ranges of the 50% lethal concentration (LC50) values of fungal filtrates were 16.60-17.78, 12.02-12.88, and 34.67-35.48 microl/ml against 1st-, 2nd-, and 3rd-stage larvae, respectively. The ranges of LC99 values were 38.90-63.10, 12.02-213.80, and 74.13-109.65 microl/ml against 1st-, 2nd-, and 3rd-stage larvae, respectively.

Animals↗

PubMed2001

[Role of gastropods in epidemiology of human parasitic diseases].

Pulmonate and prosobranch snails, being necessary hosts for parthenogenetic generations of digenetic trematodes, participate in transmission of all trematodoses important from medical point of view. Role of particular gastropods in epidemiology of these diseases is discussed in details. Invasion of land snails and slugs is mainly passive by eggs containing developed miracidia, while enter of these larvae into snails inhabiting fresh-water environments is usually active. Generations in the snail host between miracidia and cercariae vary considerable, depending upon the fluke species. Generally, the cercaria is produced by the sporocyst or the redia. Cercariae usually actively penetrate out of the infected snail and enter water. Leaving out of account cases of encystation of cercariae in external environment (liver flukes of the family Fasciolidae) and active penetration into the final host (blood flukes of the family Schistosomatidae), encystation of these larvae takes place in the second intermediate host. Cercariae of medically important flukes may develop into metacercariae in tissues of fish (liver flukes - Opisthorchis felineus, Clonorchis sinensis, intestinal flukes--Heterophyes heterophyes, Metagonimus yokogawai, Troglotrema salmincola), as well as in crustaceans (pulmonary flukes of the genus Paragonimus), insects (the bipathogenic liver fluke Dicrocoelium dendriticum and other species of the family Plagiorchiidae incidentally found in man), and gastropods (flukes of the family Echinostomatidae, among them perhaps the best known is the Oriental species--Echinostoma ilocanum). In prevention and control of human trematodoses, especially in endemic foci, elimination of snail hosts is a great importance. Using molluscides may be objectionable from the stadpoint of environmental modification through their toxicity to other organisms. Biological control of snail hosts is more attractive. It includes introduction and management of predators, parasites, or pathogens, and intramolluscan competition. Moreover, certain slugs and terrestrial snails participate in transmission of nematode larval stages, including species known as pathogenic for man - the strongylid nematodes of the genus Angiostrongylus). Such infections may be prevented by abstanding from eating raw or inadequately cooked molluscs in endemic areas.

Animals↗

PubMed1998

Biological control of Haemonchus contortus infective larvae in ovine faeces by administering an oral suspension of Duddingtonia flagrans chlamydospores to sheep.

A single oral dose of an aqueous suspension containing 11,350,000 chlamydospores of a Mexican isolate of Duddingtonia flagrans (FTHO-8) given to sheep, resulted in a maximum reduction of 88% (range 86.7-90.4%) of the population of Haemonchus contortus infective larvae in the faeces. The effect of this treatment continued for 4-5 days after administration of the suspension. The possible use of this treatment as a method of control of ovine haemonchosis is discussed.

Administration, Oral↗

PubMed1982

[Perspectives of the use of Echinostoma togoensis Jourdane et Kulo, 1981 for biological control of intestinal schistosomiasis in Africa].

A study of the experimental development of E. togoensis Jourdane et Kulo, 1981 in its successive hosts has allowed us to show that this species combines several characteristics considered to be essential with a view to biological control of intestinal schistosomiasis: --a complete and permanent sterilizing effect of Biomphalaria pfeifferi; --a pathogenicity with respect to the mollusc in infestations with more than 5 miracidia; --a very clear dominance of intramolluscal stages of Schistosoma mansoni; --ease and low cost of cycle maintenance (the parasite develops in two common hosts: the planorb and the mouse; --a high egg productivity in the mouse (10 mice infected with 75 metacercariea produce on average 620.000 eggs per day.

Africa↗

PubMed2005

Quantification and characterisation of Trichoderma spp. from different ecosystems.

Basal stem rot of oil palm caused by Ganoderma boninense is of major economic importance. Observations of the low incidence of disease due to Ganoderma species in natural stands, suggest that the disease is kept under control by some biological means. Trichoderma spp. are saprophytic fungi with high antagonistic activities against soil-borne pathogens. However, their abundance and distribution are soil and crop specific. Trichoderma species have been found to be concentrated in the A1 (0-30 cm) and Be soil horizons (30-60 cm), although the abundance of Trichoderma was not significantly different between the oil palm and non-oil palm ecosystems. Characterisation of Trichoderma isolates based on cultural, morphological and DNA polymorphism showed that T. harzianum, T. virens, T. koningii and T. longibrachiatum made up 72, 14, 10 and 4% of the total Trichoderma isolates isolated. As Trichoderma species are present in the oil palm ecosystem, but at lower numbers and in locations different from those desired, soil augmentation with antagonistic Trichoderma spp. can be developed as a strategy towards integrated management of basal stem rot of oil palm.

Arecaceae↗

PubMed2003

Seasonal translation of infective larvae of gastrointestinal nematodes of cattle and the effect of Duddingtonia flagrans: a 3-year pilot study.

A study was conducted over 3 years (1998-2000) to investigate larval availability of gastrointestinal nematodes from faeces of cattle reared under different parasite control schemes. These cattle were part of a parallel, but separate grazing trial, and were used as donor animals for the faecal material used in this experiment. At monthly intervals, faeces were collected and pooled from three groups of first-season grazing cattle. These groups were either untreated, ivermectin bolus treated or fed the nematophagous fungus Duddingtonia flagrans. The untreated and fungus treated animals were infected with gastrointestinal nematodes and the number of eggs per gram (epg) pooled faeces ranged between 50 and 700 in the untreated group and between 25 and 525 epg in the fungus treated group. Each year between June and September, artificial 1 kg dung pats were prepared and deposited on pasture and protected from birds. The same treatments, deposition times and locations were repeated throughout the study. Larval recovery from herbage of an entire circular area surrounding the dung pats was made in a sequential fashion. This was achieved by clipping samples in replicate 1/4 sectors around the dung pats 4, 6, 8 and 10 weeks after deposition. In addition, coinciding with the usual time of livestock turn-out in early May of the following year, grass samples were taken from a circular area centred where the dung pats had been located to estimate the number of overwintered larvae, which had not been harvested during the intensive grass sampling the previous year. It was found that recovery and number of infective larvae varied considerably within and between seasons. Although the faecal egg counts in 1999 never exceeded 300 epg of the faecal pats derived from the untreated animals, the abnormally dry conditions of this year generated the highest level of overwintered larvae found on herbage in early May 2000, for the 3 years of the study. Overall, biological control with D. flagrans significantly reduced larval availability on herbage, both during and between the grazing seasons, when compared with the untreated control. However, the fungus did not significantly reduce overwintered larvae derived from early season depositions (June and July), particularly when dung pats disappeared within 2 weeks after deposition. Very low number of larvae (<3 per kg dry herbage) were sporadically recovered from grass samples surrounding the ivermectin bolus faecal pats.

Animals↗