Mortierellaspecies are usually non-pathogenicfor plants or animals and humans. A rare example for a pathogen isMortierella wolfii, which is until now the only pathogen of humans and other animals.Mortierella wolfii, normally isolated from soil, rotten silage and similar substrates, causesbovine abortion,pneumoniaand systemic mycosis.[14](Wikipedia 2015)
Mortierella wolfii is a member of what was previously the Zygomycota, a group that is now being broken apart in light of genetic information.It was first discovered in India in the early 1960’s by Mehrota and Baijial.It was first described in an issue of Mycopathologia et Mycologia Applicata published in 1963 (Mortierella wolfii B.S. Mehrotra & Baijal, Mycopathologia et Mycologia Applicata 20 (1-2): 51 (1963)).It is in the kingdom Fungi, the phylum Zygomycota, the class Mucoromycotina, the order Mortierellales, the family Mortierellaceae, and, obviously, the genus Mortierella.For a short time it was moved to the genus Actinomortierella but it has now been moved back to Mortierella (Mycobank, n.d.).In 2013 Wagner, Stielow, Hoffman, Petkovits, Papp, Vágvölgyi, and Voigt preformed a molecular analysis of the entire order of Mortierellales in order to better understand their phylogeny.Their analysis found that the closest relatives of M. wolfii were M. capitata and M. ambigua. They made their analysis by examining the nuclear ribosomal DNA of the fungi.M. wolfii is not as yet well known enough to have a common name.
The morphology of M. wolfii is not very distinctive.In culture, the mycelium is white and fluffy (Davies, J. L., Ngeleka, M., & Wobeser, G. A. 2010).According to Davies et al. “hyphae were rarely septate, up to 20 μm wide with bulbous dilations with non-parallel walls and wide angle branching” (2010).The sporangiospores are ellipsoidal to kidney-shaped (Wagner et al. 2013).These spores are produced on long tapering sporangiophores that, in culture at least, seem only to be produced at high temperatures.The actual sporangia is round and very fragile, breaking apart easily to leave a bell of spores (Komoda, Itoi, Ozai, Kimura, Koizumi, & Takatori 1988).Zygospores have not been observed in this species and it appears to reproduce mainly by chlamydospore.These chlamydospores can either directly produce hyphae or can produce sporangia.The spores also seem to be highly heat resistant.This ability for the fungi to survive at very high temperatures sets it apart from other species in its genus and allows it to be highly competitive in its chosen habitat (Austwick 1976).
M. wolfii is primarily a saprobe but can become an opportunistic pathogen (Austwick 1976).Though no reference directly states it, it can be assumed that M. wolfii gets its nutrition from rotting organic matter (usually) and tissue (as a pathogen).Its pathogeny is best known from its role in mycotic abortion of bovine fetuses.This infection seems to be caused by eating rotten hay and silage where the species proliferates (Austwick 1976).This infection and others caused by M. wolfii can be termed Mucormycosis which is defined by Davey, Smith, and Kalmakoff as “an opportunistic fungal infection which usually occurs in the presence of lowered or altered host resistance and which may affect any organ of the body” (1973).Davies, Ngeleka, and Wobeser have given infection by M. wolfii the more specific name of Mortierellosis and list it as causing abortion, severe pneumonia with lesions, as well as encephalitis (2010).About 20% of the population of cows that have an M. wolfii caused abortion develop pneumonia and subsequently die (Munday et al. 2006 & Davies et al. 2010).Davies et al. believe that the pregnant cows are more susceptible to infection because the fetal tissue is conducive to spore germination (2010).Munday, Laven, Orbell, & Pandey however believe that the infection might originate in the lungs from inhaled spores and then move to the placenta and brain (2006). He also hypothesized that ruminal acidosis, where the rumen of the cow is at an unusually low pH for an extended amount of time, might be weakening the immune response of cows and making them more susceptible to the disease.Secondary lung infection is the most commonly referenced symptom of M. wolfii infection behind mycotic abortion (Davies et al. 2010, Gabor 2003, Munday et al. 2006, Komoda et al.1958).It has also been documented as causing several other types of infection.It can sometimes not cause to calf to abort but instead the calf is born infected with M. wolfii and dies soon after birth (Munday et al. 2010).It has also been shown that it likes to grow in blood vessels which is likely how it moves between the lungs, uterus and sometimes brain of the animals (Davey, Smith, & Kalmakoff 1973). There is one documented case of keratomycosis, a fungal eye infection, in a young female horse in Japan (Wada et al. 2011).There is even one uncertain case of human infection in an immune-compromised individual (Layios et al. 2014).
Several researchers have attempted to study the effects of M. wolfii more carefully.Corbes and Eades ran several experiments on mice in which they directly infected mice with the fungus.Only those who were infected cerebrally succumbed to disease.The symptoms of infection included circling, refusal of food and water, and loss of muscle control.In a few of these mice the infection moved to the lungs as well.They subjected rabbits to similar tests and found that they were much more susceptible to infection by the fungus (1991).Komoda, Itoi, Ozai, Kimura, Koizumi, and Takatori found that the major symptoms of lung infection in cows is fever, depression, and refusal of food (1988).It was also discovered by Davey, Smith, and Kalmakoff that the fungus creates a toxin that causes lethargy, constricted intestines, enlarged kidneys with lesion, and death.They were able to destroy the toxin by exposing it to the trypsin enzyme or heating it to 60 C for an hour.The toxin was not effected by an acidic pH however (1973).The toxin was identified to most likely be a protein (Davey and Kalmakoff 1974).
As mentioned, M. wolfii is primarily a saprobe and prefers to live in rotting organic matter.To be more specific it prefers “over-heated, dark colored, wet, and rotting plant material of pH 8-9” (Austwick 1976).It was found to be very prevalent in hay and silage in the later stages of decay after which anaerobic fermentation by bacteria had raised the pH significantly.It was also found in the surrounding soil (Austwick 1976).It is by eating this rotting hay and silage and breathing in its dust that cows come to be infected with M. wolfii (Austwick 1976, Munday 2006). It’s prevalence on this rotting material has lead Austwick to believe its spores may be spread by flies (1976). It was also found that the fungus prefers tissues with high oxygen contents as a pathogen (Corbel & Eades 1991).This explains why it is usually found in the uterus, lungs, and brain all of which are oxygen enriched.M. wolfii has been documented in Britain, New Zealand, Japan, Australia, Canada, and the United States (Corbel & Eades 1991, Davies et al. 2010, Komoda et al. 1988, Wada et al. 2011).I would not be surprised if the distribution extends beyond these countries but the fungus simply has yet to be recognized in other areas.
The largest impact of M. wolfii is on the dairy industry.The bearing of calves is essential in the dairy industry in order to keep the cows producing milk and to replenish the supply of female cows.Abortion is the most significant limit on calf bearing.Between twenty and thirty five percent of abortions in the dairy industry are caused by funguses (Peter 2000).M. wolfii has been recognized as a major factor in mycotic abortion only in New Zealand (Austwick 1976).However, it may be being overlooked as a cause as it is a difficult fungus to culture (Corbel & Eades 1991).PCR is making it possible to increase the incidence of identification of M. wolfii in these situations (Munday 2006).The abortions caused by M. wolfii are causing farmers to lose money, up to $1000 per abortion, and time.They are wasting money on medical expenses and will need time to rebreed the cow.They may even be forced to cull the cow which is an even bigger cost (Peter 2000).The cow may be lost to the disease as well if it comes down with pneumonia after the abortion.
There is little ecological significance for M. wolfii other than its role as a secondary decomposer of organic matter.It also does not appear to have any sort of cultural relevance.All other species of Mortierella are non-pathogenic and are being assessed for use in producing essential fatty acids but M. wolfii is not due to its pathogenic potential (Dyal & Narine 2005).The only use I could see it having the future is perhaps as a rodenticide if its toxin was further studied.Overall, humans probably would never have taken interest in M. wolfii if not for its effect on the dairy industry.
