[Contribution to the parasitic fauna of the GDR (German Democratic Republic). 7. Occurrence of Gasterophilus larvae (Diptera: Gasterophilidae) in horses].

Observations were carried out from May 1977 to May 1980 on occurrence, fauna, and seasonal dynamics of Gasterophilus spp. in 2,539 horses for butchering from all districts of the German Democratic Republic and also in 79 horses after control against gasterophilosis. 99.98% of the 13,742 second and third instar larvae of horses for butchering were Gasterophilus intestinalis, only 0.02% Gasterophilus nasalis. Out of 7,765 larvae passed after control measures Gasterophilus intestinalis dominated with more than 96%. Only in four districts of the German Democratic Republic Gasterophilus nasalis was found. The mean extensive invasion from 1977 to 1980 was 8.7%, the mean intensive invasion 33.4 +/- 3.16 larvae/infected horse, the number of larvae ranging between 2 and 576 per horse. From 1977/78 to 1979/80 the intensive invasion increased from 25.8 +/- 2.74 to 58.6 +/- 3.49 larvae/infected horse. Peaks of extensive invasion appeared in April, May and October. From October to February the horses harboured both second and third instar larvae of Gasterophilus spp. The occurrence of gasterophilosis is concentrated in the northern parts of the German Democratic Republic.