Thursday, October 23, 2014

Shot Through The Heart

A nematode? Can shoot through a heart? Yes. And it will definitely give love a bad name. 


Heartworms are a parasitic nematode and their scientific name is  Dirofilaria immitis. Listed Below is their taxonomy (Nolan 2004):

Kingdom: Animalia
                 Phylum: Nemathelminthes
        Class: Nematoda
                Order: Spiruda
                          Family: Filariidae
                                Genus: Dirofilaria


Canine heartworms are long, white skinny worms. They have a cuticle that has 3 outer layers to help protect them when they invade their hosts (Nolan 2004, Encly of Life 2011). Adult males can be 12 to 16 cm in length and have a curly posterior. The adult females are much larger, having lengths up 25 to 30 cm and have a straight posterior (Encly of Life 2011). 



Heartworms are a special parasite that require two different hosts to survive. The first host they need is called an intermediate host, and it has to be a mosquito. One study from 1970 had already identified over 60 species that served as intermediate hosts, also called a carrier or vector. The second host they need is called the definitive host, also known as the primary hosts. This definitive host can be dogs, cats, foxes, wolves, seals, coyotes, horses, bears, raccoon, wolverines, muskrats, and red pandas (Encly of Life 2011).

Life Cycle

Mature heartworms in the primary hosts lay microfilaria in the blood stream of their hosts. These microfilaria are the embryonic stages of the larvae. When a mosquito bites and eats blood from the host, it ingests these microfilaria and becomes their first host. These larvae stay in the mosquito for the first 3 larval stages, which takes about 14 days, and then they start waiting for the mosquito to bite a primary host, where they will enter through the mosquitoes bite (Nolan 2004). These microfilaria have been known to stay in a mosquito for 2 years waiting for it to bite a compatible primary host (Encly of Life 2011). After entering the primary host, they work their way towards the heart area. Heartworms do not mature until they are in the pulmonary tissue of their host, including major arteries and heart tissue (Nolan 2004). Once in the pulmonary tissues, they stay here for mating and until death. 

Heartworms cause heartworm disease, Dirofilariasis, by clogging the arteries and damaging the heart tissue of their host. Once a host has contracted heartworms, it is nearly impossible to get rid of them. Major effects of heartworm disease include coughing, exhaustion, fainting, severe weight loss, and coughing up blood (CDC 2012).


Heartworms, especially canine heartworms are fairly common around the world. They are literally found every where in the world with the exclusion of places that are relatively cold year round. To be more specific, these worms like temperate, tropical, coastal areas, and terrestrial places for living. They can be found in deserts, rainforests, swamps, lakes, savannahs, woodlands. Known regions of existence are Southern Europe, India, China, Japan, Australia, North America and South America (Encly of Life 2011).


The larvae of these nematodes eat different components of the mosquito, such as the malipighian tubes, and things in the blood the mosquito eats. As adults, the worms then feed on the blood of their hosts. 

Scary Fact: These worms have NO KNOWN PREDATORS (Encly of Life 2011). 

Testing for Heartworms

There are a few different tests that can be used to detect heartworms in a definitive host. Some of the techniques include a blood smear, antigen and antibody tests, and an ultrasound (Nolan 2004). Many times heartworms can do undectected, because after the initial infection, it takes about 200 days for microfilariae to be detected in the blood stream (Nayor and Conelly).

Here is an example of a microfilarae in a blood smear:


Center for Disease Control and Prevention. (2012). Dirofilariasis FAQs. Received from:

Encylcopedia of Life. (2011). Dirofilaria immitis: Heartworm. Received from:

Ludlam K, Jachowski L & Otto G. (1970). Potential Vectors of Dirofilaria immitis. Journal of the American Veterinary Medical Association. Vol 157 p: 1354-1359.

Nayor J and Connelly C. Mosquito-Borne Dog Heartworm Disease. SP 134: Pests in and around the Florida Home. University of Florida. Received from:

Nolan. (2004). Dirofilaria immitis Homepage. Received from:

Image Sources:

Wednesday, October 15, 2014

P. tenuis - Brainworm!

Zachary Mann

Meningeal worm, or brainworm.
Photo by DEC's Wildlife Pathology Unit

Domain: Eukaryota
Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Order: Strongylida
Family: Protostrongylidae
Genus: Parelaphostrongylus
Species: P. tenuis

Physical Description:  P. tenuis, or brainworm, is a roundworm found in the venous sinuses or subdural space of the brain (Maze and Johnstone 1986).  It normally parasitizes white tailed deer in eastern North America.  It has only been known for the past 60 years and most research done has focused on wildlife management implications.

Ecology: The brainworm is found throughout eastern North America where white-tailed deer exist, mostly deciduous and coniferous-deciduous forests.  It has been reported from Nova Scotia down to Georgia and Mississippi.  Although its normal and preferred host is the white-tailed deer, brainworm also infects moose, elk, caribou, reindeer, mule deer, goats, sheep, alpaca and even guinea pigs.  The brainworm is more often found in moist environments, but can be found anywhere deer populations inhabit.  Males and female deer are infected in equal proportions, though about 80% of affected animals are not fully mature.
Photo retrieved from Michigan
Department of Natural Resources

         The worm starts life cycle by depositing eggs around the host’s brain, or bordering blood vessels.  Once the eggs hatch and young emerge, the larvae penetrates small blood vessels and are transported into the lungs.  Once in the lungs, they enter the bronchioles and move up the respiratory tract until they reach the throat.  They are then swallowed and go through the intestinal tract, eventually coming out in a mucus coating around the deer fecal pellets.  The worm then depends on an intermediate host, gastropods, to feed on infected deer fecal matter (Duffy et al. 2002).  After a development inside the intermediate host, the larvae becomes ready for deer.  It is at this time that the parasite must get lucky and hope that a browsing or grazing deer consumes the gastropod.  Once eaten, the worm penetrates the wall of the new host’s small intestine and enters the body cavity.  Migration along nerves to the spinal cord then take place and once inside the spinal cord, the worm can begin to grow.  After a short time, they continue migrating along the spinal cord up to the subdural space surrounding the brain.  Once there the worms continues to grow into maturity and complete their life cycle. 
This maturation inside the deer takes between 80 and 90 days, at which point larvae will begin appearing in feces.  Once matured inside a deer, the brainworm can persist in a single host for many years (up to 3.7 years, probably longer), allowing many larvae to make it out into the feces (Duffy et al. 2002).  The infected white-tailed deer is usually unaffected by the brainworm, although if moose, mule deer, llama and a range of other animals be infected, death is soon to come with few ever depositing larvae in their feces.

Interesting tid-bits: As early as 1912 in Minnesota, moose were being identified as having a sickness, a disease.  It was characterized by blindness, lack of fear for humans, aimless wandering and ataxia. Analysis of diseased animals concluded irreversible damage to the central nervous system.  People knew by the 1950’s that this “moose sickness” occurred with the presence of white-tailed deer but it wasn’t until 1964 that Anderson (1964) discovered that a nematode cause the sickness!  It has since been identified as a limiting factor to moose where populations overlap with white-tailed deer (Gilbert 1974; Lankester 2010).

Literature Cited

Anderson, R.C. 1964. Neurologic disease in moose infected experimentally with Pneumostongylus tenuis from white-tailed deer. Pathologica Veterinaria 1: 289-322.

Duffy, M.S., T.A. Greaves, N.J. Keppie and M.D.B. Burt. 2002. Meningeal worm is a long-lived parasitic nematode in white-tailed deer. Journal of Wildlife Diseases 38: 448-452.

Gilbert, F.F. 1974. Parelaphostrongylus tenuis is Maine: II prevalence in moose. The Journal of Wildlife Management 38: 42-46.

Maze, R. J. and C. Johnstone. 1986. Gastropod intermediate hosts of the meningeal worm Parelaphostrongylus tenuis in Pennsylvania: observations on their ecology. Canadian Journal of Zoology 64: 185-188.

Lankester, M.W. 2010. Understanding the impact of meningeal worm, Parelaphostrongylus tenuis, on moose populations. Alces 46: 53-70.

Thursday, October 2, 2014

"Root-Knot Nematode" Meloidogyne incognita

Tori Pilger
Meloidogyne incognita
"Root-Knot Nematode"

Picture from Erwin Rose and Hein Overmars


Domain: Eukaryota
Kingdom: Metazoa
Phylum: Nematoda
Family: Meloidogynida
Genus: Meloidogyne
Species: incognita
(Singh, 2012)

Female compared to male body shape
Photo courtesy of A&T University
Physical Description: The nematode Meloidogyne incognita, or more commonly known as the root knot nematode, is a plant parasite. Because it is a plant based parasite, it has a stylet that is hollow and protrusible. This stylet secretes digestive proteins into a cell that come from their dorsal and esophageal glands (Huang et al. 2003). The stylet then sucks up the remains of the root cell into the nematode itself. It does this by using a pump-like organ at the end of a long tube that is attached to the stylet. The cutical of the male nematode is ringed. It has no lips, and its tail is blunt. The female nematode is swollen and lemon-shaped.

The root knot nematode prefers subtropical conditions with large biomass (Devran, 2009). They are found throughout the world and affect over 2,000 species of plants. This nematode is critical in the agricultural business since it is the cause of most concern when dealing with parasites that can affect ground for generations. It is of most concern when dealing with small grains, fruits, tubers, vegetables, and turf grasses (Riedel, N/A). Once an area of land is infected with this nematode, there is little one can do about getting rid of it. There are no real natural predators for this specific nematode and thus it can be nearly impossible to get rid of. Therefore it is important to discover an infection of nematodes early on by checking for stunted plant growth, discoloration, reduction of fruit/vegetable/tuber/leaf number or any other sign that might indicate plant malnourishement (Krueger, 2008). The root creates these galls or root knots where the nematode has infected the plant. These areas are caused by the female nematodes. While in the juvenile state the nematode is free living and will move about the soil until it reaches a root. The females will then latch onto the root and remain stationary. The root will grow cells around the nematode and create what is called 'giant cells' which then form the gall of the infected root (Krueger, 2008).

Interesting facts: The common name 'root-knot nematode refers to the knotted look the roots get when infected by this parasite.
Very little is actually known about how the nematode digests its food. Many of the proteins it secretes are unknown compounds that are still being studied (Devran, 2009).
This nematode was first discovered in 1855 when it was infecting the plants of a greenhouse in England (Riedel, N/A).
When cut into, an infected gall on a root will either appear purple or grey/brown in color. The purple shows an active colony of nematodes whereas a grey or brown color shows a dead one (Krueger, 2008). 


Devran, Zubeyir; Sogut, Mehmet. (June, 2009). Journal of Nematology. Distribution and Identifictaion of Root-Knot Nematodes from Turkey. Retrieved from: Pg. 1, 4. 

Huang, Guozhong; Gao, Bingli; Maier, Tom; Allen, R.; Davis, Eric; Baum, Thomas; Hussey, Richard. (Nov. 1, 2002). A Profile of Putative Parasitism Genes Expressed 
in the Esophageal Gland Cells of the Root-knot Nematode Meloidogyne incognita.Retrieved from: Pg. 1, 4.

Krueger, Romy; McSorley, Robert. (January 2008). Nematode management in Organic Agriculture. Retrieved from: Pg. 1-2.

Riedel, Richard; Miller, Sally; Rowe, Randall. (N/A). Extension Factsheet. Root Knot Nematode. Retrieved from: Pg. 1.
Singh, Sunil. (April 2012). Pathogen of the Month. Meloidogyne incognita. Retrieved from: Pg. 1.