Relationship between fecal egg counts and intestinal nematode burden of naturally infected dogs, derived from records of anthelmintic efficacy studies.

Using data collected in parasiticide efficacy studies for canine nematodes, the relation between fecal egg count (FEC) and worm burden was retrospectively explored. For the analysis, the FEC count at inclusion of the dogs into the studies and the adult nematode count established at the end of the studies, approximately 2 weeks after the FEC, were used. In total, information was available from 211, 233, 33 and 245 nematode-positive dogs of various age and sex with naturally acquired Uncinaria stenocephala (1-612 nematodes), Toxocara canis (1-91 nematodes), Toxascaris leonina (1-81 nematodes) and Trichuris vulpis (1-2780 nematodes) infections, respectively, of which 172, 195, 26 and 209 dogs, respectively, had a positive FEC. Analysis was conducted on log-transformed FEC and nematode counts to convert the data towards a normal distribution. The variables FEC, age, sex and body weight were analyzed in a linear model as predictors for the nematode count. Resulting models revealed only the FEC as significant predictor for the nematode count in all nematode species. The final linear regression model using log-transformed s accounted for 68 %, 50 %, 41 % and 39 % of the variation observed in the log-transformed burden of U. stenocephala, T. vulpis, T. leonina and T. canis, respectively (all p < 0.0001). Within the limitations of the nature of the data, these results indicate that FEC can provide useful information on the burden of common nematodes in naturally infected dogs with more value with respect to U. stenocephala and T. vulpis infections and less for ascarid infections.