Lagenidium giganteum forma caninum is an oomycete, a fungal-like organism known as water-mold, and belonging to the genus Lagenidium that causes lagenidiosis in some mammal species, characterized by progressive, severe and invasive cutaneous, subcutaneous, and disseminated infection. Clinical and pathological aspects of the disease resemble those seen in pythiosis. The first cases of lagenidiosis in mammals were officially reported in dogs in 2003. Since then, it has become increasingly recognized in dogs and cats as a cause of skin lesions.
 The genus Lagenidium was first registered in the Index Fungorum in 1857, and belongs to the family of Lagenidiaceae, order of Lagenidiales and class Oomycota. Lagenidium spp has many saprotrophic species and at least two of them responsible for cause disease in animals, L. giganteum forma caninum and L. decidium.  According to The National Center for Biotechnology Information, there are officially seven species registered within the genus, including the f. caninum, and 30 unclassified strains.
 Lagenidium spp can be found in a widely variety of hosts including algae, phytoplankton, pollen, crustaceans, and mainly as entomopathogenic organisms, formerly used for biological control of mosquitoes and nowadays deregistered by US Environmental Protection Agency. In 1999, a new specie closely associated phylogenetically with L. giganteum was diagnosed in dogs with skin infection, being taxonomically and officially recognized as forma caninum in 2013 and has been isolated from tissue lesions from mammals in the last two decades. The mainly phenotypic comparison observed between these taxa is the divergent ability to grow at mammalian body temperature (≈ 36-39 °C), strongly suggesting this feature as a key to the mammalian pathogenicity. Considering the strong relationship between Lagenidium giganteum forma caninum and L. giganteum f. giganteum, it is also suggested further investigation of host specificity and potential mammalian pathogenicity of L. giganteum f. giganteum. Other genera of oomycetes as Pythium and Phytophthora are economically important plant pathogens, and species within the genera Pyhtium, Saprolegnia, Achlya and Aphanomyces, are also animal pathogenic organisms, however there are non-reports of a plant pathogenic oomycete being also pathogenic for animals, or vice versa, including species within Lagenidium genera 
 The life cycle and habitat of L. giganteum f caninum is similar to its related species, L. giganteum, which can grow without a host. It can be found in bodies of fresh water and is observed to sustain mosquito populations. Life cycle of L. giganteum. is initiated by a biflagellate zoospore that infect a mosquito larvae host by attachment, and undergoes encystment, penetration and growth. The zoospore production can occur either by a sexual or asexual reproduction that seems to require exogenous source of sterols structurally related to cholesterol. For mycelial growth the organism kills the host by starvation. Cells can reproduce asexually while forming an exit tube, where the content migrates to the tube's tip and quick mature into zoospores, or alternately, 2 cells can fuse, forming oospores as seen in Saprolegnia sp cycle. Lagenidum giganteum can undergo a latent stage surviving for long periods (months to years). The saprophytic or vegetative stage of the oomycetes from the genus Lagenidium is characterized by filamentous mycelial growth and requires little carbon and nitrogen sources. Hyphae can survive indefinitely as a saprophyte while using energy source from rotting vegetation, dead insects or other organic material.
 Lagenidium spp colonies from mammalian strains are characterized by a colorless or yellow aerial mycelia presenting irregular radiating pattern. The mycelium has oval and spherical segments (30–40 μm), and hyphae are composed by irregular large segments of more than 400 μm, containing 1–2 discharge tubes with terminal vesicles enclosing zoospores (9–12 μm each). Encysted zoospores contain germ tubes. Broad hyphal structures of Lagenidium giganteum forma caninum can also be seen in hystopathological specimens with mean diameter, 4 μm; range, 2–7 μm, are rarely septate with nonparallel walls and irregular branching.
 The mechanism of infection for Lagenidium giganteum forma caninum and P. insidiosum in animals is similar, and also seems to be alike the host infection mechanism used for L. giganteum. The zoospores after found a suitable host, can penetrate the skin, usually in areas presenting preceding injury. One important relevant risk factor associated with the occurrence of the disease in domestic animals include swimming in contaminated lakes and ponds with potential presence of the organism. The mainly species affected with lagenidiosis are dogs and cats, and the disease has been characterized by clinical and pathological aspects that resemble those caused by P insidiosum, however often with more invasive cutaneous and subcutaneous lesions, with rapid progress and poorest response to treatment and prognosis. Cutaneous injuries are seeing as ulcerative, firm, nodular, with sinus tract and frequently encompassing lymphatic involvement, and in some cases can be macroscopically similar to cutaneous infections caused by the Chytridiomycete Basidiobolus raranarum. There are no official reports of Lagenidium giganteum forma caninum causing infection in humans but is described at least one case of human lagenidiosis caused by Lagenidium spp, developing ocular infection characterized by severe keratitis, close to lesions caused by Pythium-associated ocular disease.
 The differentiation between cutaneus and subcutaneous oomycosis from mycosis is very difficult by clinical and pathological evaluation alone, it is necessary complementary diagnostic tests to properly describe the causative agent. The definitive diagnosis of Lagenidium giganteum forma caninum is mainly based on culture, serological tests, and molecular-based diagnosis as conventional or panfungal PCR.
 While L. giganteum is susceptible to extremes temperatures (less than 8 °C and greater than 34 °C) in the environment and inside of the mosquito larvae host, as well to some pesticides compounds that include organophosphates, carbamates, herbicides, fungicides, organic solvents such as toluene and oil, there are no effective treatment in mammals for Lagenidium giganteum forma caninum. The organism responds poorly to traditional fungal therapy as for the other oomycetes. The absence of ergosterol on its cell wall makes antifungal drugs action inefficient, once the ergosterol is the main target. Reports of new drugs targeting Lagenidium spp in vitro have been studied recently, but there is still a lack of evidence of the drug's efficacy and safety in infected animals in vivo. The clinical management for the disease is currently radical surgery of the affected area.