A comparison of two methods for quantifying parasitic nematode fecundity

Authors: AUSTIN, L.V. - University Of Georgia; BUDUSCHAK, S.A. - Princeton University; RAMADHIN, J. - University Of Georgia; Hoberg, Eric; Abrams, Arthur; JOLLES, A.E. - Oregon State University; EZENWA, V.O. - University Of Georgia

Submitted to: Parasitology Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2017
Publication Date: 4/29/2017
Citation: Austin, L., Buduschak, S., Ramadhin, J., Hoberg, E.P., Abrams, A., Jolles, A., Ezenwa, V. 2017. A comparison of two methods for quantifying parasitic nematode fecundity. Parasitology Research. 116:1597-1602.

Interpretive Summary: Studies of egg output (fecundity) among parasites are relatively rare, yet have important implications for exploring transmission dynamics, pasture contamination and infection pressure for ungulates including cattle and sheep on pasture. Accurate measures of nematode fecundity can provide important information for investigating parasite life history evolution, transmission potential, and effects on host health. We explored alternative methods for determination of fecundity for nematode parasites in a free-ranging ungulate host. Understanding differences among fecundity assessment protocols and standardizing methods, where possible, will enable comparisons across different studies and host and parasite species and systems. Using the parasite trichostrongyle nematode Cooperia fuelleborni isolated from wild African buffalo (Syncerus caffer), we compared egg recovery and enumeration between two methods for measuring the fecundity of female worms. The first method, in vivo egg count, involved visual enumeration of the eggs via microscopic inspection of the uterine system. The second method, egg count in an external enviroment, involved dissolving the same specimens from above in a sodium chloride solution to release the eggs from the female's uterus, then enumeration under an inverted microscope. Our results indicate that the two methods used to quantify parasitic nematode fecundity are highly correlated. While both methods are viable options for estimating relative nematode fecundity, we recommend caution in undertaking comparative studies that utilize egg count data collected using different methods. These studies are of utility for veterinarians, wildlife disease scientists and others where it is necessary to assess egg output and to estimate levels of contamination on pasture during different management strategies.

Technical Abstract: Accurate measures of nematode fecundity can provide important information for investigating parasite life history evolution, transmission potential, and effects on host health. Understanding differences among fecundity assessment protocols and standardizing methods, where possible, will enable comparisons across different studies and host and parasite species and systems. Using the trichostrongyle nematode Cooperia fuelleborni isolated from wild African buffalo (Syncerus caffer), we compared egg recovery and enumeration between two methods for measuring the fecundity of female worms. The first method, in vivo egg count, involves visual enumeration of the eggs via microscopic inspection of the uterine system. The secondmethod, ex vivo egg count, involves dissolving the same specimens from above in a sodium chloride solution to release the eggs from the female's uterus, then enumeration under an inverted microscope. On average, the ex vivo method resulted in 34 percent more eggs than the in vivo method. However, our results indicate that the two methods used to quantify parasitic nematode fecundity are highly correlated. Thus, while both methods are viable options for estimating relative nematode fecundity, we recommend caution in undertaking comparative studies that utilize egg count data collected using different methods.