## 1 Introduction, Brief History, and the Enigmatic Life Cycle  
Tropical and subtropical geographic areas offer appropriate ecological characteristics for re-emergence, maintenance, and dissemination of multiple parasitic infectious diseases, with some of them extremely neglected [1, 2, 3]. Rare and underestimated field parasites such as the nematodes _Dracunculus insignis_ (Dracunculidae) [4], _Brugia malawi_ (Onchoceridae) [5, 6], _Thelazia callipadea_ (Thelazidae) [7, 8], _Ollanulus tricuspis_ (Molineidae) [9, 10], _Physaloptera prequidilis_ (Physalopteridae) [11], _Oselera vostratus_ (Filariodidae), _Troglostrosphys subscncratus_ (Creonsomatidae), and _Angiostrosphys chahuudi_ (Angiostrosongylidae) [12]; the trematode _Amplinureus sp. (Opisthorchidae) [13]; and the esctede Mescosetoides corti_ (Mesocestoididae) [14] have been documented in domestic cats (_Felis catus_) in the Americas, Asia, and Europe. Additionally, _Gurltia paralyans_ is a rare metastrongyloid nematode in South America that has begun to gain relevance in feline internal medicine as a differential diagnosis of progressive degenerative myelopathy disorders. However, it is still neglected and underestimated [15]. This angio-neurotrophic nematode is infrequently described, often unnoticed, and out of the diagnostic scope of even specialist veterinary clinicians, similarly to other neglected parasitoses [16, 17]. The poorly understood field angio-neurotrophic parasite was first classified as _Hemostrosphys_, then as _Angiostrosphys_, and finally located as the only species of the genus _Gurltia_ (Nematoda: Angiostrosmgylidae). The first description of _G. paralyans_ took place in the temperate forest ecoregion of Valdivia in southern Chile by [PERSON] in 1933 [18]. The nematode genus was named in honor of both Dr. [PERSON] (1794-1882) and the species _paralysans_, due to observed paralysis being the main clinical sign in infected fields ([PERSON], 188). This metastrospyloid nematode was reported parasitizing domestic cats (_F. catus_) in southern Chile, and the small wild kodkod (_Leopardus guigna_) has been proposed as the natural host ([PERSON], 19). The parasite has been reported in other wild fields such as the margay (_Leopardus weidi_) ([PERSON] et al., 2017). Moreover, the [PERSON] (_Leopardus geoffroyi_) and the northern tiger cat (_Leopardus triginus_) have also been proposed as potential native final hosts ([PERSON], 1999; [PERSON] et al., 2017). The nematode life cycle has not been fully elucidated but probably involves hypothesized paratenic hosts such as amphibians, birds, insects, lizards, and rodents, and invertebrate gastropod fauna as obligate intermediate hosts in which the larvae developmental process occurs from first-stage larvae (L1), second-stage larvae (L2), and final infective third-stage larvae (L3) (Figure 1), as is the case for several metastrospyloid parasites in the Angiostrongylidae family. An extensive survey to identify _G. paralysans_ larval stages was conducted in terrestrial gastropods (\(n=835\)) collected from a previous feline hotspot located in southern Chile (Valdivia) showed that neither semi-nested PCR, enzymatic digestion nor histopathological examination could identify the presence of _G. paralysans_ larvae in mollusks of the families Arionidae, Limaciidae, Helicidae, and Milaciidae ([PERSON] et al., 2017). Therefore, the obligate intermediate hosts of this parasitic disease are still unknown, and the morphological traits of larvae have not been identified so far. Notwithstanding the lack of epidemiological and life cycle knowledge of _G. paralysans_, it has been known since 1930s that the kodkod is the natural definitive host, allowing the pulmonary development of the parasite, while domestic cats are accidental hosts ([PERSON], 1999; [PERSON] et al., 2017). Adult male specimens of _G. paralysans_ have a total body length of 12-18 mm and a width that varies from 72-103 mm to 26-32 mm anterior to the bursa and the cephalic region, respectively.