Mixed Infections of Species of Leucocytozoon in Individual Birds from Atlantic Canada

Abstract

In a survey of the hematozoa of passeriform birds from New Brunswick and insular Newfoundland, 12.3% of the birds from New Brunswick and 3.9% of those from Newfoundland harbored mixed infections of Leucocytozoon dubreuili, L. majoris, and L. fringillinarum. Infections were scattered through all the families of birds surveyed, but were particularly common in the Bombycillidae and Paridae. The conclusion is drawn that the identification of species of Leucocytozoon on the basis of its host alone is not valid and that morphological criteria must be employed for specific diagnoses. In a survey of the hematozoa of the passeriforms from insular Newfoundland (Bennett et al., 1974), a high proportion of infection with two or more species of Leucocytozoon in the same individual was noted. Further surveys of passeriforms from New Brunswick (Bennett et al., 1975) indicated a similar situation. This report examines in greater detail the prevalence of such multiple infections of species of Leucocytozoon in individual birds. MATERIALS AND METHODS Birds were captured in mist nets and smears were obtained as previously described (Bennett, 1970). The bird samples were primarily obtained from the Avalon Peninsula in insular Newfoundland (Bennett et al., 1974) and from the Tantramar Marsh area of New Brunswick (Bennett et al., 1975). RESULTS AND DISCUSSION The species of Leucocytozoon commonly infecting the passeriform birds of Atlantic Canada are Leucocytozoon fringillinarum Woodcock 1910, L. dubreuili Mathis and Leger 1911 and L. majoris (Laveran 1902). These species are considered to be valid taxa by a variety of authors, including Fallis et al. (1974), Hsu et al. (1973), Khan and Fallis (1970, 1971), and Bennett and Campbell (1975), on the basis of both morphological and life history evidence. These species have usually been considered to be specific for certain families (Bennett and Laird, 1973; Fallis et al., 1974; Hsu et al., 1973). Thus L. dubreuili is restricted to the Turdidae (Khan and Fallis, 1970; Fallis and Bennett, 1966), L. majoris to the Paridae, and L. fringillinarum to a variety of passeriform families. There are virtually no records other than those of Bennett et al. (1974, 1975) that suggest that more than one species of Leucocytozoon occur in an individual bird, although similar records for Plasmodium are abundant. There is no particular reason, however, why the situation so commonly recorded for Plasmodium should not also apply to Leucocytozoon, especially as both genera are members of the Haemosporidida. Identification of the leucocytozoids is largely predicated on host specificity (at the familial level) and the morphology of the mature gametocytes in the peripheral circulation. The first aspect is based on somewhat limited experimental evidence (Clarke, 1965; Fallis and Bennett, 1966; Khan and Fallis, 1970, 1971). The latter aspect is the basis of all species descriptions. The morphological characters usually used to define species are the size and shape of the parasite (ovoid or round), the shape of the host-parasite complex (fusiform or round), and the shape of the host cell nucleus as characteristically distorted by the parasite-a series of characters well sumsummarized and illustrated by Fallis et al. (1974). The three parasites considered in this study can all be characterized as round and in rounded cells and differ in the appearance of the parasite-induced distortion of the host cell nucleus. Thus L. fringillinarum is characterized by a caplike host cell nucleus (Figs. 1, 3, 5, 7, 8), L. dubreuili by a host cell nucleus consisting of a thin band connecting two inflated terminal bulbs (Figs. 2, 4, 6, 8), and L. majoris by a thin band of host nuclear material extending more than halfway about the circumReceived for publication 29 April 1975.