First record of Macrobilharzia (Digenea: Schistosomatidae) from Phalacrocorax lucidus in South Africa, with molecular evidence suggesting a distinct species

Abstract

Schistosomatid flukes are mainly found in the vascular system of their definitive hosts. Avian schistosomatids, represented by 13 genera, are blood parasites affecting snails and aquatic birds in their larval and adult stages, respectively, with the genus <i>Macrobilharzia</i> Travassos, 1922 being a poorly documented clade, with limited records globally. During a parasitological investigation, adult schistosomatids (prevalence = 57%) were recovered from the intestinal mesenteric veins of white-breasted cormorants (<i>Phalacrocorax lucidus</i>; n = 14), sampled during July 2024 and March 2025 at Loskop Dam, Mpumalanga Province, South Africa. These flukes were identified as <i>Macrobilharzia</i> sp. based on morphological and molecular characterisation. Males are large and flat, measuring up to 28 mm in length, with a maximum width of 2.2 mm in the first quarter of the body. The gynaecophoric canal extends from the ventral sucker to the end of the body, and the ventral sucker is larger than the oral sucker. The oesophagus bifurcates into caeca in front of the ventral sucker and extends to the posterior end of the body, uniting to form the common caecum close to the posterior end of the worm. The number of testes varies in size, ranging from 104 to 184. The <i>28S rDNA</i> gene sequence generated from this study (accession number: PX973526) showed a 99% homogeneity with Schistosomatidae sp. (KF672860) from <i>Indoplanorbis exustus</i> in Nepal, and 94% homogeneity with <i>Macrobilharzia macrobilharzia</i> (AY858885) from <i>Anhinga anhinga</i> in North America. The phylogenetic analyses in the current study positioned the specimen in a well-supported <i>Macrobilharzia</i> clade, forming a distinct lineage from <i>M. macrobilharzia</i>. This constitutes the first documented record of the genus from southern Africa and the first report from <i>P</i>. <i>lucidus</i>. The observed molecular divergence, together with its phylogenetic placement, suggests that the material may represent a distinct species within the genus. The record extends the known geographical distribution of the <i>Macrobilharzia</i> genus, highlighting significant gaps in knowledge regarding avian schistosomatid diversity in African aquatic ecosystems. These findings contribute to baseline parasite biodiversity data and emphasise the need for integrative surveys (morphological and molecular characterisation) to better understand host-parasite dynamics in these piscivorous birds and associated ecosystems.