Eimeria phocae sp. n. from the Harbor Seal (Phoca vitulina Concolor)

Abstract

Oocysts are 43.9 by 26.6 ,um with micropyle, oocyst residuum, and polar granule. Gametogeny occurs in the colon and to a lesser degree in the distal ileum. The patent period is 11 days. Pathology involves bloody diarrhea, necrotizing hemorrhagic colitis, and death. It is the first protozoan parasite described from the harbor seal. No protozoan parasites have been reported from marine mammals in the literature including the comprehensive checklist of marine mammal parasites prepared by Dailey and Brownell (1972). The purpose of this paper is to describe a new coccidium, Eimeria phocae sp. n., which has been isolated and characterized from two young harbor seals (Phoca vitulina concolor). MATERIALS AND METHODS Two young harbor seals, 1 male and 1 female, estimated to be about 2 months of age, were captured in Portland, Maine, USA, on 20 June 1972. They were then transferred to the Johns Hopkins University School of Hygiene and Public Health, and housed together in the same tank. They were fed a ration of frozen mackerel. On 11 August 1972, the male died of severe coccidiosis after a 2-day illness. A complete necropsy was performed. On 4 September 1972, the female seal developed diarrhea and began passing large numbers of coccidial oocysts, which were uniform in shape, size, and color. The oocysts were identical to those found in the intestinal mucosal scrapings of the dead male tank-mate. Fresh fecal samples from this animal were collected at 8to 12-hr intervals until fecal examinations for oocysts were negative. The feces were homogenized in tap water, strained through a double layer of cheesecloth, and mixed with a thin layer of a 2.5% potassium dichromate solution in a petri dish which was incubated at 26 C for 1 week so that the oocysts could sporulate. The preparations were then microscopically examined for sporulation at 8to 10hr intervals. Sporulated oocysts were concentrated by flotation with Sheather's sugar solution, examined and measured microscopically under a 95 X apochromatic objective. Composite drawings were based on the details compiled from many oocysts. Received for publication 9 July 1973. RESULTS Oocysts of a new species of Eimeria were present in a pure infection in both harbor seals. Detailed descriptions and drawings of the oocysts (Fig. 1), gametogony stages, and pathogenicity are given below. Eimeria phocae sp. n. (Figs. 1-10) Description Unsporulated (Fig. 2) and sporulated oocysts (Figs. 3, 4) ellipsoidal or slightly ovoid. Oocyst