Sex-inducing effects toward planarians widely present among parasitic flatworms.

Various parasitic flatworms infect vertebrates for sexual reproduction, often causing devastating diseases in their hosts. Consequently, flatworms are of great socioeconomic and biomedical importance. Although the cessation of parasitic flatworm sexual reproduction is a major target of anti-parasitic drug design, little is known regarding bioactive compounds controlling flatworm sexual maturation. Using the planarian Dugesia ryukyuensis, we observed that sex-inducing substances found in planarians are also widespread in parasitic flatworms, such as monogeneans and flukes (but not in tapeworms). Reverse-phase HPLC analysis revealed the sex-inducing substance(s) eluting around the tryptophan retention time in the fluke Calicophoron calicophorum, consistent with previous studies on the planarian Bipalium nobile, suggesting that the substance(s) is likely conserved among flatworms. Moreover, six of the 18 ovary-inducing substances identified via transcriptome and metabolome analyses are involved in purine metabolism. Our findings provide a basis for understanding and modifying the life cycles of various parasitic flatworms.

Morphological and molecular characterization of Calicophoron raja (Näsmark, 1937) collected from wild Bovidae in South Africa.

Paramphistomes, commonly known as rumen flukes, are digenean parasites that infect ruminants. Accurate morphological identification of paramphistome species is challenging and often neglected. For instance, it requires sagittal midline sections of adult flukes, which are difficult to prepare. Therefore, the majority of the genetic information on paramphistomes found in the International Nucleotide Sequence Database is not supported by morphological descriptions, and the DNA barcodes of paramphistome species remain unreliable. In the present study, both morphological and molecular characterizations were simultaneously performed to ensure the reliability of the DNA information for the paramphistome species Calichophoron raja (Näsmark, 1937). The morphological characteristics of the sagittal and horizontal sections of adult flukes from a black wildebeest (Connochaetes gnou) and a waterbuck (Kobus ellipsiprymnus) in South Africa were identical to those previously described for Ca. raja. Additionally, this study represents a new host record of the species from Co. gnou. All sequences of the internal transcribed spacer 2 region of ribosomal DNA were 100% identical among the 18 flukes analyzed in the present study. A single nucleotide mutation was observed between Ca. raja in this study and Ca. raja detected in domestic ruminants in Kenya.

Leptospiral meningoencephalitis in a raccoon dog.

Neuroleptospirosis is a rare disease caused by pathogenic Leptospira interrogans in humans; however, it has not been fully studied in animals. A young wild raccoon dog was found convulsing in the recumbent position and died the next day. Histologic examination revealed nonsuppurative meningoencephalitis in the cerebrum, cerebellum, midbrain, and medulla oblongata. The lesions consisted of mixed infiltrates of Iba1-positive macrophages and CD3-positive T cells, with a small number of CD79α-positive B cells and myeloperoxidase-positive neutrophils. In the frontal cortex, perivascular cuffs and adjacent microglial nodules were distributed diffusely, especially in the molecular layer. Glial nodules were comprised of Iba1- and myeloperoxidase-positive activated microglia. Immunohistochemistry revealed leptospires in mononuclear cell perivascular cuffs, but not in glial nodules. Neuroleptospirosis was accompanied by Leptospira-related nonsuppurative interstitial nephritis, pulmonary edema and hemorrhage, and coronary periarteritis, as well as Toxocara tanuki in the small intestine and nonspecific foreign-body granulomas in the lungs and stomach.