Acanthocheilonema is a genus within the family Onchocercidae which comprises mainly tropical parasitic worms.Merrian Webster. 2020. https://www.merriam-webster.com/medical/Acanthocheilonema#:~:text=Medical%20Definition%20of%20Acanthocheilonema,parasitic%20in%20humans%20and%20monkeys Cobbold created the genus Acanthocheilonema with only one species, Acanthocheilonema dracunculoides, which was collected from aardwolf (Proteles cristatus: Hyaenidae) in the region of South Africa in the nineteenth century.Cobbold TS. "Description of a new generic type of entozoon from the aard wolf (Proteles); with remarks on its affinities, especially in reference to the question of parthenogenesis". Proceedings of the Zoological Society of London 1870;1:9–14 These parasites have a wide range of mammalian species as hosts, including members of Carnivora, Macroscelidea, Rodentia, Pholidota, Edentata, and Marsupialia. Many species among several genera of filarioids exhibit a high degree of endemicity in studies done on mammalian species in Japan.Yamaguti S. "Studies on the helminth fauna of Japan". Part 35. Mammalian nematodes II. Japanese Journal of Zoology 1941; 9:409–439.Yagi K, Bain O, Shoho C. "Onchocerca suzukii n. sp. and O. skrjabini (=O. tarsicola) from a relict bovid, Capricornis crispus, in Japan". Parasite 1994; 1:349–356. However, no concrete evidence has confirmed any endemic species in the genus Acanthocheilonema.
There are about fifteen well characterized parasitic species found in genus Acanthocheilonema. A. delicata n. sp. (2013), A. dracunculoides (Cobbold 1870), A. filaria (Kou, 1958), A. mansonbahri (Nelson, 1961), A. mephitis (Webster and Beauregard, 1964), A. odendhali (Perry, 1967), A. pachycephalum (Ortlepp, 1961), A. pricei (Vaz and Pereira, 1934), A. procyonis (Price, 1955), A. reconditum (Grassi, 1889), A. sabanicolae (Eberhard and Campo-Aasen, 1986), A. setariosa (Mönnig, 1926), A. spirocauda (Leidy, 1858), A. viteae (Krepkogorskaja, 1933), and A. weissi (Seurat, 1914) are the well characterized parasitic species found all around the world in variety of hosts. Some of the crucial parasites that affect a wide range of host species are discussed below.
Acanthocheilonema delicata Acanthocheilonema delicata was discovered and characterized from an endemic badger species (Meles anakuma) in Japan. The researchers identified the DNA sequences of mitochondrial cytochrome c oxidase subunit 1 (cox1) gene in the Japanese badgers. Morphologically, filarioids analyzed were identified as thin, small and delicate and in females the length was longer (twice as in males). Anterior of the filarioids is slightly bulbous having two sets of four papilla (worms) and amphids. They possess distinct buccal cavity with buccal capsule consisting of a thick buccal ring. The esophagus is divided into short anterior muscular portion and long, posterior glandular portion. Caudal extremity in both males and females consists of three conical lappets. The location of the parasitic adult worms in the host species (Meles anakuma) was found to be the subcutaneous connective tissue, whereas the microfilaria was found in the skin. Data taken from the Genbank of fourteen species of genus Acanthocheilonema compared to the newly found species for possible similarities and distinctions shown in the table below:
+ Comparison of morphological characteristics of Acanthocheilonema parasites Species → A. delicata A. dracunculoides A. odendhali A. reconditum A. spirocauda A. viteae Body length Female-22–38; Male-10–16μm Female-38.5–45.2; Male-21.7–24μm Female-100-150; Male-46-64μm Female-20.7-25.5; Male-9.3-17.1μm Female-155; Male-87μm Female-49μm; Male-38μm Body width at mid-body Female-85-140;Male-60-85μm Female-220-280;Male-140-160μm Female-348-415;Male-228-281μm Female-146-168;Male-92-100μm Female-660;Male-400μm Female-230-350;Male-155-165μm Total esophagus length Female-3000–4125;Male-2520–3350μm Female-1940–2500;Male-1960–2170μm Female-1782–2197;Male-1890–2251μm Female-2040–2340;Male-1860–2040μm Female-1300–1800;Male-1900–2000μm Female-1370-1570;Male-1600-1660μm Tail Female-167–250;Male-113–162μm Female-240–395;Male-140–180μm Female-214–322;Male-147–245μm Female-180–300;Male-80–145μm Female-260;Male-230μm Female-320–470;Male-280μm No. of terminal lappets 3 3 3 3 Female-3; Male-4 3 Microfilariae width 7-9μm 4.5-5.2μm 3.5μm 4.5μm 4-4.5μm 4.5μm Microfilariae body length 153–180μm 121-218μm 231-249μm 270μm 266-302μm 180-200μm Host animal Meles anakuma Proteles cristatus and spotted hyaena Zalophus californianus Crocuta crocuta and Hyaena hyaena Phoca vitulina concolor Meriones libycus Parasitic location of adult worms Subcutaneous connective tissue Peritoneal cavity Intermuscular fascia Subcutaneous connective tissue Pulmonary artery and right ventricle Subcutaneous tissue Parasitic location of microfilariae Skin Blood blood blood blood blood locality Japan Kenya California, US Italy, India, US, Kenya, Japan coastal Maine, US Iran Reference M. Rioche "Présence de Dipetalonema dracunculoides (Cobbold, 1870) chez le chien dans la région d'Alger". Archives de l'Institut Pasteur d'Algérie, 38 (1960), pp. 386-398G.S. Nelson "Dipetalonema dracunculoides (Cobbold, 1870), from the dog in Kenya: with a note on its development in the louse-fly, Hippobosca longipennis". Journal of Helminthology, 37 (1963), pp. 235-240 M. L. Perry "A new species of Dipetalonema from the California sea lion and a report of microfilaria from a steller sea lion (Nematoda: Filarioidea)" Journal of Parasitology, 53 (1967), pp. 1076-1081M. L. Perry, D. J. Forrester "Dipetalonema odendhali (Nematoda: Filarioidea) from the northern fur seal, with a description of the microfilaria" Journal of Parasitology, 57 (1971), pp. 469–472 G. S. Nelson "Dipetalonema reconditum (Grassi, 1889) from the dog with a note on its development in the flea, Ctenocephalides felis and the louse, Heterodoxus spiniger". Journal of Helminthology, 36 (1962), pp. 297-308 R.C. Anderson "The taxonomy of Dipetalonema spirocauda (Leidy, 1858) n. comb. (= Skrjabinaria spirocauda) and Dirofilaria roemeri (Linstow, 1905) n. comb. (= Dipetalonema roemeri)". Canadian Journal of Zoology, 37 (1959), pp. 481-493R.C. Anderson Nematode parasites of vertebrates: Their development and transmission, CABI Publishing, CAB International, Wallingford Oxon UK (2000), pp. 494-496A.G. Chabaud "Le genre Dipetalonema Diesing 1861; Essai de classification". Annales de Parasitologie Humaine et Comparée, 27 (1952), pp. 250-285T.A. Krepkogorskaja "Beitrag zur Fauna der Nematoden aus Rhombomys opimus Licht. aus Kasakstan". Zoologischer Anzeiger, 102 (1933), pp. 87-91M.D. Sonin "Filariata of Animals and man and diseases caused by them, Part 3, Filariidae, Onchocercinae". Fundamentals of Nematology, vol. 24, Nauka Publishers, Moscow (1975)
Acanthocheilonema dracunculoides
Acanthocheilonema dracunculoides Cobbold, a species discovered in 1870, is a nematode parasitic worm particularly found in domestic dogs and other carnivores like aardwolf, spotted hyaena and red fox.Schwan, Volker & Schröter, F. (2007). "First record of Acanthocheilonema dracunculoides from domestic dogs in Namibia". Journal of the South African Veterinary Association. 77. 220-1. 10.4102/jsava.v77i4.381. These parasites can be located on various continents like Europe, Asia and Africa.Sonin M D 1975 Filariata of animals and man and diseases caused by them. Part III. Filariidae, Onchocercinae. Amerind Publishing, New Delhi it is known to be endemic in Morocco, Algeria, Tunisia, Mali, Niger, Democratic Republic of Congo, Sudan, Somalia, Kenya, Tanzania and South Africa.Baylis H A 1929 A Manual of Helminthology Medical and Veterinary. Baillière, Tindall and Cox, LondonGedoelst L 1916 "Notes sur la faune parasitaire du Congo Belge". Revue Zoologique Africaine 5: 1–90Macchioni G 1982 "Ancylostomiasis of wild carnivore and visceral larva migrans in man". Acta Mediterranea di Patologia e Tropicale 1 (1. Suppl.): 125–127Morel P C 1959 "Les helminthes des animaux domestiques de l'Afrique occidentale". Revue d'Élevage et de Médecine Vétérinaire des Pays Tropicaux 12: 153–174Nelson G S 1963 "Dipetalonema dracunculoides (Cobbold, 1870), from the dog in Kenya: with a note on its development in the louse-fly, Hippobosca longipennis". Journal of Helminthology 37: 235–240Nelson G S, Heisch R B, Furlong M 1962 "Studies in filariasis in East Africa II. Filarial infections in man, animals and mosquitoes on the Kenya coast". Transactions of the Royal Society of Tropical Medicine and Hygiene 56: 202–217 This parasite follows an indirect life cycle. In the carnivore species, the male and female parasite tend to be biased to exist mainly in the peritoneal cavity.Ortega-Mora L M, Rojo-Vázquez F A 1988 "Sobre la presencia de Dipetalonema dracunculoides (Cobbold, 1870) en el perro en España". Revista Ibérica de Parasitología 48: 187–188 Males are typically shorter and are 15–32 mm long and 0.1–0.2 mm wide, whereas females are almost double, standing at 30–60 mm long and 0.1–0.3 mm wide in diameter.Fraga de Azevedo J 1943 "On the presence of Dipetalonema dracunculoides (Cobbold 1870) among dogs in Portugal". Contribution to the study of its morphology. Anais do Instituto de Medicina Tropical 1: 105–114Jansen J, Peeters M E, Boersema J H, CremersHJWM 1988 Dipetalonema dracunculoides (Cobbold 1870) (Nematoda: Onchocercidae) bij een geïmporteerde hond. Tijdschrift vir Diergeneeskunde 113: 537–538 Sexually mature female parasites of A. dracunculoides are viviparous, they produce L1-stages, known as microfilariae, which eventually appear in the peripheral blood. Microfilariae are unsheathed and measure 185–276 μm (length) by 4.2–6 μm (width)Rao MAN 1938 "Dipetalonema dracunculoides (Cobbold, 1870)". The Indian Journal of Veterinary Science and Animal Husbandry 8: 127–130Sonin M D 1975 Filariata of animals and man and diseases caused by them. Part III. Filariidae, Onchocercinae. Amerind Publishing, New Delhi Although the final host is the carnivores for A. dracunculoides there are some other intermediate hosts that are involved in the parasite life cycle. Louse fly Hippobosca longipennis and the hard tick Rhipicephalus sanguineus, also known as dog tick, have been identified as intermediate hosts that helps the parasite to complete its life cycle.Olmeda-García A S, Rodríguez-Rodríguez J A, Rojo-Vázquez F A 1993 "Experimental transmission of Dipetalonema dracunculoides (Cobbold 1870) by Rhipicephalus sanguineus (Latreille 1806)". Veterinary Parasitology 47:339–342 Although Acanthocheilonema dracunculoides has a reputation of not being an endemic parasite in the domestic dogs, recent evidence of the presence of the parasite in domestic animals show some signs of pathogenicity. As mostly these parasites are considered innocuous in the dogs, recent studies and evidence from Spain suggests that the parasite is not completely harmless and innocuous in the domestic dogs as believed earlier.Valcárcel F, Ferre I, Gómez-Bautista M, Rojo-Vázquez F A 1990 "Diagnóstico de laboratorio de la infestación por Dirofilaria immitis en el perro". Medicina Veterinaria 7: 345–353Bolio M E, Montes A M, Gutierrez C, Alonso F D, Bernal L J, Sauri C H, RodríguezVivas R I 2002 "Hallazgos clínicos en perros parasitados por Dipetalonema dracunculoides". Archivos de medicina veterinaria 34: 283–286