{{Short description|Genus of roundworms}} {{Italic title}} {{Automatic taxobox | name = ''Acanthocheilonema'' | taxon = Acanthocheilonema}}
'''''Acanthocheilonema''''' is a genus within the family Onchocercidae which comprises mainly tropical parasitic worms.<ref>Merrian Webster. 2020. https://www.merriam-webster.com/medical/Acanthocheilonema#:~:text=Medical%20Definition%20of%20Acanthocheilonema,parasitic%20in%20humans%20and%20monkeys</ref> 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.<ref>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</ref> 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.<ref>Yamaguti S. "Studies on the helminth fauna of Japan". Part 35. Mammalian nematodes II. ''Japanese Journal of Zoology'' 1941; 9:409–439.</ref><ref>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.</ref> 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.<ref name="autoRefA" /> 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.<ref name="autoRefA">{{cite journal|doi=10.1016/j.parint.2012.08.004|title=''Acanthocheilonema delicata'' n. sp. (Nematoda: Filarioidea) from Japanese badgers (''Meles anakuma''): Description, molecular identification, and Wolbachia screening|year=2013|last1=Uni|first1=Shigehiko|last2=Bain|first2=Odile|last3=Suzuki|first3=Kazuo|last4=Agatsuma|first4=Takeshi|last5=Harada|first5=Masashi|last6=Motokawa|first6=Masaharu|last7=Martin|first7=Coralie|last8=Lefoulon|first8=Emilie|last9=Fukuda|first9=Masako|last10=Takaoka|first10=Hiroyuki|journal=Parasitology International|volume=62|issue=1|pages=14–23|pmid=22926421}}</ref> 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.<ref name="autoRefA" /> 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:
{| class="wikitable" |+ 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 || <ref name="autoRefA" /> ||<ref>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. 386-398</ref><ref>G.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</ref> || <ref>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. 1076-1081</ref><ref>M. 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</ref>|| <ref>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</ref> ||<ref>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. 481-493</ref><ref>R.C. Anderson ''Nematode parasites of vertebrates: Their development and transmission'', CABI Publishing, CAB International, Wallingford Oxon UK (2000), pp. 494-496</ref>||<ref>A.G. Chabaud "Le genre ''Dipetalonema'' Diesing 1861; Essai de classification". ''Annales de Parasitologie Humaine et Comparée'', 27 (1952), pp. 250-285</ref><ref>T.A. Krepkogorskaja "Beitrag zur Fauna der Nematoden aus Rhombomys opimus Licht. aus Kasakstan". ''Zoologischer Anzeiger'', 102 (1933), pp. 87-91</ref><ref>M.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)</ref> |}
==''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.<ref>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.</ref> These parasites can be located on various continents like Europe, Asia and Africa.<ref>Sonin M D 1975 ''Filariata of animals and man and diseases caused by them. Part III. Filariidae, Onchocercinae''. Amerind Publishing, New Delhi</ref> it is known to be endemic in Morocco, Algeria, Tunisia, Mali, Niger, Democratic Republic of Congo, Sudan, Somalia, Kenya, Tanzania and South Africa.<ref>Baylis H A 1929 ''A Manual of Helminthology Medical and Veterinary''. Baillière, Tindall and Cox, London</ref><ref>Gedoelst L 1916 "Notes sur la faune parasitaire du Congo Belge". ''Revue Zoologique Africaine'' 5: 1–90</ref><ref>Macchioni G 1982 "Ancylostomiasis of wild carnivore and visceral larva migrans in man". ''Acta Mediterranea di Patologia e Tropicale'' 1 (1. Suppl.): 125–127</ref><ref>Morel P C 1959 "Les helminthes des animaux domestiques de l'Afrique occidentale". ''Revue d'Élevage et de Médecine Vétérinaire des Pays Tropicaux'' 12: 153–174</ref><ref>Nelson 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: 235–240</ref><ref>Nelson 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</ref> 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.<ref>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</ref> 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.<ref>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: 105–114</ref><ref>Jansen 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</ref> 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)<ref>Rao MAN 1938 "''Dipetalonema dracunculoides'' (Cobbold, 1870)". ''The Indian Journal of Veterinary Science and Animal Husbandry'' 8: 127–130</ref><ref>Sonin M D 1975 ''Filariata of animals and man and diseases caused by them. Part III. Filariidae, Onchocercinae''. Amerind Publishing, New Delhi</ref> 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.<ref>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</ref> 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.<ref>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: 345–353</ref><ref>Bolio 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</ref>
The discovery of ''Acanthocheilonema'' parasites in the non-endemic species has triggered more research in this field. ''Dirofilaria immitis'', ''D. repens'', ''Acanthocheilonema dracunculoides'' and ''A. reconditum'' are the common species that have been known to be found in canine filarial nematodes. These nematodes present blood circulating microfilariae which are differentiated to the species level using the techniques like PCR and by acid phosphatase activity patterns.<ref>{{cite journal|doi=10.1186/1756-3305-6-48|title=Morphometric analyses of canine blood microfilariae isolated by the Knott's test enables ''Dirofilaria immitis'' and ''D. Repens'' species-specific and ''Acanthocheilonema'' (Syn. ''Dipetalonema'') genus-specific diagnosis|year=2013|last1=Magnis|first1=Johannes|last2=Lorentz|first2=Susanne|last3=Guardone|first3=Lisa|last4=Grimm|first4=Felix|last5=Magi|first5=Marta|last6=Naucke|first6=Torsten J.|last7=Deplazes|first7=Peter|journal=Parasites & Vectors|volume=6|article-number=48|pmid=23442771|pmc=3598535 |doi-access=free }}</ref> ''A. reconditum'' and ''A. dracunculoides'' live in the peritoneal cavity and adipose tissue of the host species and are less pathogenic,<ref>Lindemann BA, Evans TL, McCall JW: "Clinical responses of dogs to experimentally induced ''Dipetalonema reconditum'' infection". ''American Journal of Veterinary Research''. 1983, 44: 2170-2172</ref> however ''D. immitis'' and ''D. repens'' are considered to be the emerging agents of parasitic zoonoses and are continuously expanding their ranges in the European. areas.<ref>Genchi C, Kramer LH, Rivasi F: "Dirofilarial infections in Europe". ''Vector-Borne and Zoonotic Diseases'' 2011, 10: 1307–1317</ref>
==''Acanthocheilonema odendhali''==
The filarial worm ''Acanthocheilonema odendhali'' was first discovered in 1967 from the California California sea lion ''Zalophus californianus''.<ref>Perry ML (1967) "A new species of Dipetalonema from the California sea lion and a report of Microfilariae from a Steller sea lion (Nematoda: Filarioidea)". ''Journal of Parasitology'' 53(5):1076–1081</ref> This species was found inhabiting the intermuscular fascia and thoracic and the abdominal cavities. Initially this species was described in the ''Dipetalonema'' genus as ''Dipetalonema odendhali'', however due to later evidences it was transferred to the genus ''Acanthocheilonema''.<ref>Chabaud AG, Bain O (1976) "La lignée ''Dipetalonema''. Nouvel essai de classification". ''Annales de Parasitologie Humaine et Comparee'' 51(3):365–397</ref> ''A. odendhali'' was subsequently found in other marine species like Steller sea lion (''Eumetopias jubatus'') and northern fur seal (''Callorhinus ursinus'').<ref>Nikolskij OR (1969) "On the parasite fauna of fur seals in pelagic period of their life". In: ''Problemy Parazitologii''. ''Proceedings of the 6th Scientific Conference of Parasitologists of the USSR'', part 1, Kiev, Naukova Dumka: 179–184 {{in lang|ru}}</ref><ref>Dailey MD, Hill BL (1970) "A survey of metazoan parasites infecting the California (''Zalophus californianus'') and Steller (''Eumetopias jubatus'') sea lion". ''Bulletin of the Southern California Academy of Sciences'' 69:126–132</ref> Besides the ''A. odendhali'', other filarioidean species such as ''A. spirocauda'', commonly known as heart-worm has also been identified as parasitic in phocids.<ref>Leidernberger S, Boström S (2008) "Characterization of the heartworm ''Acanthocheilonema spirocauda'' (Leidy, 1858) Anderson, 1992 (Nematoda: Onchocercidae) in Scandinavia". ''Parasitology Research'' 104:63–67</ref><ref>Dunn JL, Wolke RE (1976) "''Dipetalonerna spirocauda'' infection in the Atlantic harbor seal (''Phoca vitulina concolor'')". ''Journal of Wildlife Diseases'' 12:531–538</ref>
''A. odendhali'' was primarily reported in the northern fur seals on the island of Pribilof Archipelago in 1967.<ref>Perry ML, Forrester DJ (1971) "''Dipetalonema odendhali'' (Nematoda: Filarioidea) from the northern fur seal, with a description of the microfilaria". ''Journal of Parasitology'' 57(3):469–472</ref> Prior to that two scientists Mark C. Keyes and Eugene T. Lyons had discovered the microfilariae in the blood of subadult male seals and adult filarioids and microfilariae in the samples collected from the blubber, fur, and the skin from these male seals.<ref>Keyes MC (1964) ''Research in fur seal mortality, St. Paul Island, Alaska. 8 July to 24 September 1963''. US Department of the Interior, US Fish and Wildlife Service, Marine Mammal Biology Lab, Seattle, Washington</ref> In these studies, the prevalence and the intensity of these species were not examined. The life cycle of ''A. odendhali'' is still unknown. However, according to the National Marine Mammal Laboratory, Northwest and Alaska Fisheries Center (NWAFC) reports, some blood-sucking flies or insects that infest the wounds are potential intermediate hosts (vectors) in their life cycle.<ref>NWAFC Processed Report 81-2 (1981) ''Fur Seal Investigations'', 1980. National Marine Mammal Laboratory, Northwest and Alaska Fisheries Center, National Marine Fisheries Service, NOAA, Seattle, Washington</ref> Pathogenicity of ''A. odendhali'' was however not studied in these experiments and research but this parasite is considered as non-pathogenic.<ref>Anderson RC (2000) Nematode parasites of vertebrates: their development and transmission, 2nd ed. CABI, Wallingford</ref> In 2011 and 2012, a study that investigated helminths of northern fur seals on Saint Paul Island in Alaska discovered that ''A. odendhali'' was a parasite on the seals.<ref name="AutoRefB">{{cite journal|doi=10.1007/s00436-013-3483-3|title=Ecological, morphological, and molecular studies of ''Acanthocheilonema odendhali'' (Nematoda: Filarioidea) in northern fur seals (''Callorhinus ursinus'') on St. Paul Island, Alaska|year=2013|last1=Kuzmina|first1=T. A.|last2=Kuzmin|first2=Y. I.|last3=Tkach|first3=V. V.|last4=Spraker|first4=T. R.|last5=Lyons|first5=E. T.|journal=Parasitology Research|volume=112|issue=9|pages=3091–3100|pmid=23760875|s2cid=17545069}}</ref> Other research done by the same group investigated the intensity and prevalence of the parasite and discovered that prevalence of adult ''A. odendhali'' parasites in the fur seals was 18 percent; the intensity depends on the individual host species and the seven parasite specimens found in the parasite. Average intensity of infection was approximately 1.32 ±0.83 SD, whereas the abundance was found to be 0.24 SD.<ref name="AutoRefB" />
==''Acanthocheilonema reconditum''==
''Acanthocheilonema reconditum'' is a non-pathogenic canine helminth parasite of the specialized connective tissue. It is distributed in the same endemic areas as D. immitis, which is also known as heart-worm.<ref>G. M. Urquhart, J. Armour, J. L. Duncan, A. M. Dunn, F. W. Jennings ''Veterinary Parasitology'' (2nd ed.), Blackwell Science (1996), p. 307</ref><ref>D. D. Bowman, R. C. Lynn, M. L. Eberhard, A. Alcaraz. ''Georgi's parasitology for veterinarians'' (8th ed.), Saunders, St. Louis, MO (2003), p. 422</ref> Although it is endemic to some areas mentioned earlier, but the parasite is widely distributed as it has been identified in other species and around different continents. Dogs are frequently parasitized by the filarids. This transmission is usually carried out by the flea species and lice species. Flea vectors include species such as ''Ctenocephalides canis'', ''Pulex irritans'', ''Pulex simulans'', and ''Echidnophaga gallinacea'', whereas the lice species include Linognathus setosus and Heterodoxus spiniger. These vectors are infected with the ''A. reconditum'' parasite with the microfilariae during the blood repast in a parasitized dog. These species act as intermediate hosts in completing the life cycle of the parasite.<ref name="autoRefC">Otranto D, Torres FT, Brianti E et al. (2013) "Vector-borne helminths of dogs and humans in Europe". ''Parasites & Vectors'' 6:1–14</ref> These microfilariae develop onto an infectious stage during the L3 (larvae stage 3) stage in the digestive tract of these vectors from where they can be inoculated into the new host. The third stage larvae could be found as soon as 7 days after the appearance of the vectors on the donor host species.<ref>D.R. Farnell, D.R. Faulkner "Prepatent period of ''Dipetalonema reconditum'' in experimentally-infected dogs". ''Journal of Parasitology'', 64 (3) (1978), pp. 565-567</ref> (L3) Once it enters the new host species, the microfilariae develops into the adult stage. Most of these adult stage parasites are located in the subcutaneous tissue.<ref>Leite LC, Luz E, Cirio SM et al (2012) "Infection in domestic dogs (''Canis lupus familiaris'', Linnaeus, 1758) from Guaratuba, Paraná, Brazil by circulating microfilariae of ''Acanthocheilonema reconditum'' (Grassi, 1889)". ''Semina: Ciencias Agrarias'' 33(3):1149–1155</ref> Although the infection by ''A. reconditum'' does not exhibit any clinical signs, a treatment to limit dissemination is primarily recommended. Recent studies of ''A. reconditum'' occurrence in the southern regions of Italy has shown prevalence of this parasite as high as 13.3% with an annual incidence rate of 5.9%, which was observed in naturally exposed dogs.<ref name="autoRefD" /> Recent experiments have enhanced scientific knowledge of the biology and ecology of this parasite. The full development of microfilariae occurs in the experimental infected cat flea ''Ctenocephalides felis felis'' in about 15 days. Localization and size of this parasite in this infected flea suggests the possibility that this might act as an intermediate host throughout the ingestion of the infected fleas rather than inoculation of the blood meal on dogs.<ref name="autoRefD">Napoli, E., Gaglio, G., Falsone, L. et al. "New insights into the biology and ecology of ''Acanthocheilonema reconditum'' (spirurida: onchocercidae)". ''Parasites & Vectors'' 7, O29 (2014). https://doi.org/10.1186/1756-3305-7-S1-O29</ref><ref name="autoRefC" /> Ivermectin (0.25 mg/kg) is a drug that is preferred to treat infection by this parasite.<ref>Lindemann BA, Mccall JW (1893) "Microfilaricidal activity of ivermectin against ''Dipetalonema reconditum''". ''Journal of Veterinary Pharmacology and Therapeutics'' 6:74–76</ref> As microfilariae of this parasite are mainly found in the blood, they are often mistaken for other parasites like ''Dirofilaria immitis''. It is therefore crucial to identify and distinguish between them using modified Knott's procedure.<ref>''Acanthocheilonema reconditum''. 2017. https://capcvet.org/guidelines/acanthocheilonema-reconditum/</ref> ==''Acanthocheilonema spirocauda''==
''Acanthocheilonema spirocauda'', also known as seal heartworm, is a filarial parasite that primarily infects the phocid seals, including ''Phoca vitulina'' (Harbor seal). The Heartworm was originally described as ''Filaria spirocauda'' by Leidy.<ref>Leidy J (1858) Contributions to helminthology. Proc Acad Nat Sci Philadelphia 10:110–112</ref> Eventually ''Acanthocheilonema'' was raised to generic level and this species settled under this genus, and a researcher Anderson presented its current name.<ref name="autoRefE">Anderson RC (1992) ''Nematode parasites of vertebrates. Their development and transmission'', 2nd edn. CABI, Wallingford</ref> ''A. spirocauda'' is found in the heart of the seals, and that is why is got its name 'Heartworm'.<ref name="autoRefE" /> While there is no significant threat to the seal populations due to this parasite as of now, however the infection with this parasite can result in pathological consequences like in the case of ''D. immitis'', which includes the characteristics such as anorexia, fatigue, heart and lung complications, and potentially death.<ref name="auto 18062474">{{cite journal|doi=10.3354/dao01823|title=Phocid seals, seal lice and heartworms: A terrestrial host parasite system conveyed to the marine environment|year=2007|last1=Leidenberger|first1=S.|last2=Harding|first2=K.|last3=Härkönen|first3=T.|journal=Diseases of Aquatic Organisms|volume=77|issue=3|pages=235–253|pmid=18062474|doi-access=free}}</ref> Researchers suggest that these parasites share strong evolutionary basis with its phocid hosts about some 45 million years ago<ref name="auto 18062474" /> It is believed to be transmitted via the seal louse ''(Echinophthirius horridus)''.<ref>{{cite journal|doi=10.1139/z81-197|title=The seal louse, Echinophthirius horridus: An intermediate host of the seal heartworm, ''Dipetalonema spirocauda'' (Nematoda)|year=1981|last1=Geraci|first1=J. R.|last2=Fortin|first2=J. F.|last3=Aubin|first3=D. J. St.|last4=Hicks|first4=B. D.|journal=Canadian Journal of Zoology|volume=59|issue=7|pages=1457–1459|bibcode=1981CaJZ...59.1457G }}</ref> The prevalence of the parasite in the host species is approximately 8.8%, and intensity ranges up to 44 specimens per heart.<ref name="autoRefF">{{cite journal|doi=10.1007/s00436-008-1159-1|title=Characterization of the heartworm ''Acanthocheilonema spirocauda'' (Leidy, 1858) Anderson, 1992 (Nematoda: Onchocercidae) in Scandinavia|year=2008|last1=Leidenberger|first1=Sonja|last2=Boström|first2=Sven|journal=Parasitology Research|volume=104|issue=1|pages=63–67|pmid=18762981|s2cid=11394725}}</ref>
Additional researchers have investigated its additional potential hosts and global distribution patterns of this parasite. Studies discovered some additional hosts of this parasite that include ribbon seal ''P. fasciata'', harp seal ''P. groenlandica'', ringed seal ''P. hispida'', Baltic ringed seal ''P. h. botnica'', Ladoga seal ''P.h. ladogensis'', spotted seal ''P. largha'', hooded seal ''Cystophora cristata'', and bearded seal ''Erignathus barbatus''.<ref name="autoRefG">Westerling B, Stenman O, Rudbäck E (2005) "Pathology of seals from the Finnish coastal waters, Lake Saimaa and Lake Ladoga in the years 1982–2004". ''Proceedings from the Symposium on Biology and Management of Seals in the Baltic area'', 15–18 February 2005, Helsinki, pp 76–79</ref> The primary sites of infection in the hosts are the right and left ventricles of the heart, pulmonary vein, pulmonary artery, and vena cava.<ref name="autoRefF" /> These parasites are widely distributed around the globe. They can be found in the Northern Hemisphere and Holarctic realm.<ref name="autoRefG" /><ref>Leidenberger S, Hårding K, Härkönen T (2007) "Phocid seals, seal lice and heartworms: a terrestrial host–parasite system conveyed to the marine environment". ''Diseases of Aquatic Organisms'' 77:235–253</ref> The present localities of ''A. spirocauda'' include the Danish North Sea (Agger Tange), Limfjord (Thy), Skagerrak (Lysekil) and Kattegat (Rungsted, Lille Vrøj), and the Baltic Sea (Lunds høje, Falster).<ref name="autoRefF" />
==''Acanthocheilonema viteae''== ''Acanthocheilonema viteae'' is a filarial nematode that infects rodent species.<ref>Anderson, R. C. ''Nematode Parasites of Vertebrates: Their Development and Transmission''. 2nd Ed. New York, NY: CABI Publishing, 2000. {{isbn|978-0-85199-421-5}}</ref>{{page number needed|date=October 2024}} ''A. viteae'' is also used as a model species in the research experiments in order to study human filarial infections.<ref>Babila Tachu, Smitha Pillai, Richard Lucius, Thomas Pogonka ''Infection and Immunity''. Dec 2007. "Essential Role of Chitinase in the Development of the Filarial Nematode Acanthocheilonema viteae". 76 (1) 221-228; {{doi|10.1128/IAI.00701-07}}</ref> The natural hosts for this parasite are gerbils, whereas the experimental hosts include hamsters, jirds (''Meriones unguiculatus'', also known as Mongolian gerbils), and ''Mastomys'' species.<ref>Johnson MH, Orihel TC, Beaver PC. 1974. "Dipetalonema viteae in the experimentally infected jird, ''Meriones unguiculatus''. I. Insemination, development from egg to microfilaria, reinsemination, and longevity of mated and unmated worms". ''Journal of Parasitology'' 60:302–309.</ref> The vector that aids to finish its life cycle is a soft tick named ''Ornithodoros tartakovskyi'' (natural) and ''Ornithodoros moubata'' (experimental vector).<ref>Lucius R, Textor G, Kern A, Kirsten C. 1991. "''Acanthocheilonema viteae'': vaccination of jirds with irradiation-attenuated stage-3 larvae and with exported larval antigens". ''Experimental Parasitology'' 73:184–196</ref> The adults of ''A. viteae'' reside in the deep subcutaneous tissue, whereas the microfilariae circulate in the blood.<ref>Neilson JT. 1978. "Primary infections of ''Dipetalonema viteae'' in an outbred and five inbred strains of golden hamsters". ''Journal of Parasitology'' 64:378–380.</ref> These worms are known to modulate the host immunological systems, however they do not prohibit the immunological pathways entirely. It renders them increased survival. An excretory product called ES-62 is secreted by ''A. viteae'' and is homologous to ones produced by nematodes that infect humans but not those of non-parasitic species. ES-62 molecules tend to exhibit anti-inflammatory actions, using a phosphorylcholine-bearing moiety to affect the intracellular pathways that are associated with the antigen receptors and TLR-dependent cell responses.<ref>Miguel A. Pineda, Felicity Lumb, Margaret M. Harnett, William Harnett, "ES-62, a therapeutic anti-inflammatory agent evolved by the filarial nematode ''Acanthocheilonema viteae''", ''Molecular and Biochemical Parasitology'', Volume 194, Issues 1–2, 2014, Pages 1-8, {{issn|0166-6851}} {{doi|10.1016/j.molbiopara.2014.03.003}}</ref>
In nature, during the third larvae infected stage, ''A. viteae'' parasites are transferred to their mammalian hosts with the aid of vector ''Ornithodoros tartakovskyi''. In the mammalian host, the L3 stage develops to mature adults and generates the microfilariae, which are again ingested by ticks. After reaching L3, parasites transfer to mammalian hosts via arthropods' mouth parts.<ref>Morris, C. P., et al. "A Comprehensive, Model-Based Review of Vaccine and Repeat Infection Trials for Filariasis". ''Clinical Microbiology Reviews'' 26 (2013): 381-421. {{PMID|23824365}}.</ref><ref>Anderson, R. C. ''Nematode Parasites of Vertebrates: Their Development and Transmission''. 2nd ed. New York, NY: CABI Publishing, 2000.</ref> Various stages of ''A. viteae'' have two chitinase protein bands, one of 205 kDa and 68 Kda. Studies reveal that the 205 kDa band of stage L3 was an oligomer formed of 68kDa monomers.<ref>Adam, R., B. Kaltmann, W. Rudin, T. Friedrich, T. Marti, and R. Lucius. 1996. "Identification of chitinase as the immunodominant filarial antigen recognized by sera of vaccinated rodents". ''Journal of Biological Chemistry'' 271:1441-1447.</ref> Chitin has been reported as a component of the eggshells of these nematodes.<ref>Wharton, D. 1980. "Nematode egg-shells". ''Parasitology'' 81:447-463.</ref> Chitinase plays a vital role in the third larvae stage (L3) and female worms, as its inhibition during these stages leads to have increased mortality. There are no safe and efficient drugs to eliminate these infections so far but chitin is seen as a potential target for the development of anthelmintic drugs and vaccines.<ref>{{cite journal|doi=10.1128/IAI.00701-07|title=Essential Role of Chitinase in the Development of the Filarial Nematode Acanthocheilonema viteae|year=2008|last1=Tachu|first1=Babila|last2=Pillai|first2=Smitha|last3=Lucius|first3=Richard|last4=Pogonka|first4=Thomas|journal=Infection and Immunity|volume=76|issue=1|pages=221–228|pmid=17938220|pmc=2223640}}</ref> Intracellular bacteria ''Wolbachia'' are prevalent among the different species of nematodes. However, ''Wolbachia'' is absent in ''Acanthocheilonema viteae''. Since ''A. viteae'' lacks ''Wolbachia'', it is widely used as a negative control for experiments investigating the bacterium.<ref>Michelle Michalski. 2015. Stage L3 ''Acanthocheilonema viteae'', Infective Larvae, Harvested from ''Ornithodoros tartakovsky''. BEI resources</ref><ref>{{cite journal |last1=Risch |first1=F |last2=Ritter |first2=M |last3=Hoerauf |first3=A |last4=Hübner |first4=MP |title=Human filariasis-contributions of the Litomosoides sigmodontis and Acanthocheilonema viteae animal model. |journal=Parasitology Research |date=December 2021 |volume=120 |issue=12 |pages=4125–4143 |doi=10.1007/s00436-020-07026-2 |pmid=33547508|pmc=8599372 }}</ref> Their role in the pathology of filarial infections and symbiotic nature with host makes it potential target to intervene in filarial infections in humans.<ref>{{cite journal|pmid=12866789|year=2003|last1=Hartmann|first1=N.|last2=Stuckas|first2=H.|last3=Lucius|first3=R.|last4=Bleiss|first4=W.|last5=Theuring|first5=F.|last6=Kalinna|first6=B. H.|title=Trans-species transfer of ''Wolbachia'': Microinjection of ''Wolbachia'' from ''Litomosoides sigmodontis'' into ''Acanthocheilonema viteae'' |journal=Parasitology |volume=126|issue=Pt 6 |pages=503–11 |doi=10.1017/S0031182003003172|s2cid=21227697 |url=http://edoc.hu-berlin.de/18452/28563 }}</ref>
== References == {{Reflist}}
{{Taxonbar|from=Q16747049}}
Category:Spirurida Category:Parasitic nematodes of mammals