Determination of the specific gravity of eggs of equine strongylids, Parascaris spp., and Anoplocephala perfoliata.

The study investigates the specific gravity of eggs from three types of horse parasites: equine strongylids, Parascaris spp., and Anoplocephala perfoliata. Researchers found that the specific gravity varied among the parasite egg types, which has implications for how to best test and treat these parasites in horses.

Study Overview and Methodology

The need for this study arises from the escalating resistance to anthelmintic treatments (medicines that expel or kill parasites) among livestock. Veterinarians use fecal egg counts to decide when to treat for parasites but it is important to know the density of different parasite eggs in order to accurately count them. The common practice in equine veterinary medicine is to use a flotation medium with a specific gravity of 1.20 or more. However, the specific densities of horse parasite eggs haven’t been extensively examined.

• The researchers made different concentration trials of glucose-salt solutions with different specific gravities (ranging from 1.06 to 1.16 in the first trial, and from 1.02 to 1.10 in the second one).
• Each of the solutions was layered according its density in the centrifuge tubes.
• Concentrated mixtures of each of the three types of parasite eggs were placed on the top of the tubes.
• The tubes were then centrifuged and each layer of the solution pipetted out and placed onto an egg counting slide.
• Each egg type found on the slide was assigned to a specific gravity, based on the layer it was gathered from.

Study Results and Implications

They found that the three types of eggs had statistically different specific gravities. The study provides the first specific gravity data for two egg types: strongylid and Anoplocephala perfoliata. Notably, the specific gravity of tapeworm eggs lay between strongylid and Parascaris spp. densities.

• Mean egg Specific Gravity (SG) of Anoplocephala perfoliata was 1.0636 (with a 95% confidence interval of 1.0629-1.0642).
• Parascaris spp. eggs had a mean SG of 1.0903 (with a 95% confidence interval of 1.0897-1.0909).
• Strongylid egg SG averaged to 1.0453 (with a 95% confidence interval of 1.0448-1.0458).

This research is significant because it fills in gaps of knowledge regarding specific egg gravity, allowing for improvements in the accuracy of fecal egg counting methods. It also directs future research into other possible causes for poor tapeworm egg recovery in equine fecal samples, which can lead to underdiagnosis and untreated infestations.