MINI-BAERMANN FUNNEL, A SIMPLE DEVICE FOR CLEANING NEMATODE INFECTIVE LARVAE

The Baermann filter method is a long-standing, simple technique for recovering nematodes from soil and charcoal coprocultures. Material containing the nematodes is placed on a mesh screen lined with several layers of tissue paper or cheesecloth, and the screen is placed in the mouth of the funnel. Rubber tubing attached to the funnel stem is clamped, and water is added to submerge the material. The filtration material allows the nematodes to swim through while holding back the substrate. Over time the nematodes settle at the clamp in the tubing. After several hours, the clamp is opened and water containing the nematodes is collected. Although recovery of the nematodes is efficient, they are often contaminated with soil or charcoal debris, requiring a secondary cleaning by sedimentation or filtration. Described here is a small, simplified version of the Baermann apparatus that can be used as a secondary cleaning device. The "mini-Baermann" is constructed from materials commonly found in the laboratory. Experiments using infective larvae of 3 nematode species demonstrated that the majority of the larvae applied to the device are collected within 2 hr, and nearly all by 4 hr. Dead larvae fail to pass through the filter and do not significantly impact the passage of living larvae. In addition to removing debris from nematode suspensions, this device can rapidly and efficiently separate living, motile larvae from dead larvae.

Semi-quantitative differentiation of cyathostomin larval cultures by reverse line blot

Cyathostomins are the most prevalent horse nematodes worldwide and over 50 species are described. The eggs and the infective larvae (L3) can easily be obtained or cultured from infected horses, but cannot be differentiated morphologically at species level. A reverse line blot (RLB) method based on the hybridization of a PCR fragment with a species specific probe, has previously been developed for the differentiation of individual eggs and/or L3s, but is too labor intensive for large scale studies. In the present study a RLB method on multiple pooled L3s for the semi-quantitative differentiation of cyathostomin larval cultures was developed and validated. First, the probability of the presence of a certain species within a pool was calculated as function of the frequency and the number of L3s within a pool. Ten L3s per pool were found to be optimal. Next, the probability, the chance of occurrence was calculated when 4 pools per culture were used. The probability distributions for 0, 1, 2, 3 or 4 positive pools were transformed into the corresponding median frequency of the cumulative probability: 0.014, 0.04, 0.08, 0.16 and 0.59, respectively. Based on these calculated probabilities, RLB on 10 L3s per pool and 4 pools per sample was validated by estimating the cross-hybridization, precision and accuracy in 3 groups of horses. First, absence of cross-hybridization was confirmed by differentiation of the same L3s (160 L3s from the 4 horses from group 1) in the RLB on individual as well as on pooled L3s. Cross-hybridization was excluded for 9 of the most common cyathostomins. Next, the precision and accuracy were determined by the differentiation of 10 replicates of 3 cultures from 3 horses from group 2 (1200 L3s). The coefficient of variation (CV) was between 0 and 0.90 and the accuracy was between 0.42 and 1.73. A Monte Carlo simulation based on the observed scores and associated probability distributions gave similar results as the use of a fixed median frequency. The LPGs obtained from 276 larval culture counts from a larger cohort (23 horses, group 3) were not significantly different from the LPGs obtained from summation of the LPG per species found by RLB on pooled L3s. The RLB on pooled L3s was found therefore an useful semi-quantitative method for the differentiation of the most common cyathostomin L3, with a workload of approximately one tenth of that of the RLB on individual L3s.

Duddingtonia flagrans in the control of gastrointestinal nematodes of horses

Horses can harbor a large amount of parasites that may cause serious clinical signs even death. The aim of this study was to evaluate the predatory activity of the fungus Duddingtonia flagrans against infective larvae (L3) of gastrointestinal nematodes of horses in fecal culture. The experimental design was completely randomized with three treated groups (G1, G2 and G3) and one control (CG), using eight animals/group. The treated animals received G1: 1.5 × 10(5); G2: 3 × 10(5) and G3: 6 × 10(5) chlamydospores of D. flagrans/kg body weight during 21 days. The fungi preparation was given at every other three-day interval. Faecal samples were collected during 30 days, on the same interval, to perform the fecal egg counts (EPG) and fecal culture for each horse. All groups demonstrated similar results for the EPG (P > 0.05) counts. D. flagrans significantly reduced (P < 0.05) the number of infective larvae after 72 h-interval between treatments. The G2 and G3 promoted higher results (P < 0.05) of L3 reduction compared to the CG. The biological control with the predacious fungi D. flagrans is still a promising free-living parasite regulator alternative to be use in livestock.