Roundworms have complex life cycles involving eggs passed in feces that develop into infective larvae. Puppies, kittens, and young animals are most commonly infected through prenatal, nursing, or environmental exposure. Roundworm larvae migrate through tissues before maturing and reproducing in the intestines, completing their life cycles. Regular deworming is especially important for hunting or outdoor animals to prevent roundworm infection and spread.

1. Round wormsRound worms
Life cyleLife cyle

2. What are they?What are they?
 Roundworms are big worms. Typically theyRoundworms are big worms. Typically they
are white, about the diameter of aare white, about the diameter of a
spaghetti-strand and about 4 inches inspaghetti-strand and about 4 inches in
length. Often times kittens or puppieslength. Often times kittens or puppies
vomit one up or we are horrified when wevomit one up or we are horrified when we
see them in the feces.see them in the feces.

4.  Kittens or puppies may be born withKittens or puppies may be born with
roundworms! We know that Roundwormroundworms! We know that Roundworm
larva are tiny enough to migrate throughlarva are tiny enough to migrate through
the placental blood supply to the fetal liverthe placental blood supply to the fetal liver
or lungs. Soon after birth the juvenileor lungs. Soon after birth the juvenile
roundworms begin migrating from the liverroundworms begin migrating from the liver
and lungs to the intestine where they growand lungs to the intestine where they grow
to adults and begin laying eggs. Withinto adults and begin laying eggs. Within
three weeks after birth, puppies and kittensthree weeks after birth, puppies and kittens
can begin shedding roundworm eggs intocan begin shedding roundworm eggs into
the environment.the environment.

6.  A second source of infection is through theA second source of infection is through the
mother's milk - Roundworm larva can gainmother's milk - Roundworm larva can gain
entry into the mammary glands and then beentry into the mammary glands and then be
passed to the puppies or kittens as theypassed to the puppies or kittens as they
nursenurse
 A third possibility is if the young animalA third possibility is if the young animal
should eat an embryonated egg found inshould eat an embryonated egg found in
fecal contamination of food or water bowls,fecal contamination of food or water bowls,
the nesting box or other environmentalthe nesting box or other environmental
sources. The egg hatches within thesources. The egg hatches within the
intestine and a "Blood-Lung" migrationintestine and a "Blood-Lung" migration
begins as described below.begins as described below.

8. dogsdogs
 There are two species of roundwormsThere are two species of roundworms
affecting dogs and puppies: Toxocara canisaffecting dogs and puppies: Toxocara canis
and Toxascaris leonina. Both are treatedand Toxascaris leonina. Both are treated
with the samewith the same medicationmedication protocol so whenprotocol so when
eggs are seen on a fecal flotation exam, it iseggs are seen on a fecal flotation exam, it is
not necessary to determine which species isnot necessary to determine which species is
present.present.

10.  Regular deworming is especiallyRegular deworming is especially
recommended for dogs that hunt and mightrecommended for dogs that hunt and might
consume the flesh of hosts carrying wormconsume the flesh of hosts carrying worm
larvae. Puppies are frequently simply assumedlarvae. Puppies are frequently simply assumed
to be infected and automatically dewormedto be infected and automatically dewormed
 . If a dog or puppy vomits up a worm, there is. If a dog or puppy vomits up a worm, there is
a good chance this is a roundworm (especiallya good chance this is a roundworm (especially
in a puppy). Roundworms are long, white andin a puppy). Roundworms are long, white and
described as looking like spaghetti.described as looking like spaghetti.
Tapeworms can also be vomitedTapeworms can also be vomited

14.  Worm Species in CattleWorm Species in Cattle
Cattle host over 14 different species of gastro-Cattle host over 14 different species of gastro-
intestinal roundworms. Different species live inintestinal roundworms. Different species live in
different locations in the intestine. As there aredifferent locations in the intestine. As there are
usually just a few of these roundworms present, theusually just a few of these roundworms present, the
harm they cause is not always apparent and can beharm they cause is not always apparent and can be
difficult to assess.difficult to assess.
Four species live in the abomasum:Four species live in the abomasum:
 barber pole worm (barber pole worm (Haemonchus placeiHaemonchus placei))
 brown stomach worms (brown stomach worms (Ostertagia ostertagiOstertagia ostertagi andand O.O.
bisonisbisonis))
 threadworm (threadworm (Trichostrongylus axeiTrichostrongylus axei))

16.  Life Cycle of Roundworms cattleLife Cycle of Roundworms cattle
Although some details vary, the life cycle ofAlthough some details vary, the life cycle of
all the gastro-intestinal roundworms of cattleall the gastro-intestinal roundworms of cattle
follows a similar pattern (Figure 1):follows a similar pattern (Figure 1):
 1.Female roundworms lay microscopic eggs1.Female roundworms lay microscopic eggs
that pass in the manure of cattle.that pass in the manure of cattle.
 2.Within a few days, a free-living larva2.Within a few days, a free-living larva
develops and hatches from the eggdevelops and hatches from the egg

18.  .3.The hatched larva develops through a second, and.3.The hatched larva develops through a second, and
then a third stage where it becomes capable ofthen a third stage where it becomes capable of
infecting cattle. Larval development on pasture takesinfecting cattle. Larval development on pasture takes
only a few days in warmer months, but takes severalonly a few days in warmer months, but takes several
weeks during cooler weatherweeks during cooler weather
 .4.Cattle become infected with roundworms as they.4.Cattle become infected with roundworms as they
graze on pasture or by ingesting food or watergraze on pasture or by ingesting food or water
contaminated with manure containing infectivecontaminated with manure containing infective
larvae.larvae.
 5.The larvae mature in the intestine and then mate.5.The larvae mature in the intestine and then mate.
The females begin shedding eggs within two to fourThe females begin shedding eggs within two to four
weeks after being ingested by the cow.weeks after being ingested by the cow.

20.  When do Cattle Become Infected?When do Cattle Become Infected?
Roundworms live for approximately one yearRoundworms live for approximately one year
in cattle. As the previous year's adults die, theyin cattle. As the previous year's adults die, they
are replaced by a new generation of parasites.are replaced by a new generation of parasites.
This stage generally occurs from June toThis stage generally occurs from June to
August. This annual cycle has two high pointsAugust. This annual cycle has two high points
for egg output: one in the spring and one in thefor egg output: one in the spring and one in the
late summer/early autumnlate summer/early autumn

22. Life cycle horsesLife cycle horses
 Lifecycle of the common internal parasitesLifecycle of the common internal parasites
Worms living in the tissues and the gut are trueWorms living in the tissues and the gut are true
parasites, using the horse’s body as a source ofparasites, using the horse’s body as a source of
nutrition and lodging. Initially, minute larval stagesnutrition and lodging. Initially, minute larval stages
migrate through the gut wall and undergomigrate through the gut wall and undergo
development (moults) within the body tissues, blooddevelopment (moults) within the body tissues, blood
vessels and organs. Even a small number of worms invessels and organs. Even a small number of worms in
these stages can cause severe and permanent internalthese stages can cause severe and permanent internal
damage. Unfortunately, during this migratory perioddamage. Unfortunately, during this migratory period
(up to 6 months for Bloodworms) the larval stages are(up to 6 months for Bloodworms) the larval stages are
not controlled by all worming compounds.not controlled by all worming compounds.

24.  The worms do not multiply in the horse’s bodyThe worms do not multiply in the horse’s body
but through microscopic eggs passed in thebut through microscopic eggs passed in the
manure. Studies have shown that up to 99% ofmanure. Studies have shown that up to 99% of
a worm population exists as eggs or larvae ona worm population exists as eggs or larvae on
the pasture or in stable bedding. Worm eggsthe pasture or in stable bedding. Worm eggs
either hatch to produce minute larvaeeither hatch to produce minute larvae
(Bloodworms, Small Redworms) or develop(Bloodworms, Small Redworms) or develop
into infective eggs on the pasture (Largeinto infective eggs on the pasture (Large

26.  It is important that all persons responsible forIt is important that all persons responsible for
the health care of horses have anthe health care of horses have an
understanding of the common worms and howunderstanding of the common worms and how
to control them. Regular worm control ofto control them. Regular worm control of
internal parasites is important to ensure properinternal parasites is important to ensure proper
digestive efficiency and freedom from worm-digestive efficiency and freedom from worm-
related conditions.related conditions.
Heavy worm burdens can lead to recurringHeavy worm burdens can lead to recurring
colic, poor condition, lack of thrift, chronic orcolic, poor condition, lack of thrift, chronic or
acute diarrhoea, poor stamina and coatacute diarrhoea, poor stamina and coat
condition, and lack of performance in horsescondition, and lack of performance in horses
of all agesof all ages

28. Life cycle catsLife cycle cats
 There are two species of roundworms affectingThere are two species of roundworms affecting
cats and kittens:cats and kittens: Toxocara catiToxocara cati andand ToxascarisToxascaris
leoninaleonina. Both are treated with the same. Both are treated with the same
medication protocol so when eggs are seen onmedication protocol so when eggs are seen on
a fecal flotation exam it may not be necessarya fecal flotation exam it may not be necessary
to determine which species is present.to determine which species is present. T.T.
leoninaleonina can infect both dogs and cats socan infect both dogs and cats so
identifying this roundworm might be helpful inidentifying this roundworm might be helpful in
indicating which pets in the household are atindicating which pets in the household are at
risk for further contagionrisk for further contagion

30. HOW DO WE KNOW IF A CAT ISHOW DO WE KNOW IF A CAT IS
INFECTED?INFECTED?
 Regular deworming is especiallyRegular deworming is especially
recommended for cats that hunt and mightrecommended for cats that hunt and might
consume the flesh of hosts carrying wormconsume the flesh of hosts carrying worm
larvae. Kittens are frequently simply assumedlarvae. Kittens are frequently simply assumed
to be infected and automatically dewormed.to be infected and automatically dewormed.
 If a cat or kitten vomits up a worm, there is aIf a cat or kitten vomits up a worm, there is a
good chance this is a roundworm (especially ingood chance this is a roundworm (especially in
a kitten). Roundworms are long, white anda kitten). Roundworms are long, white and
described as looking like spaghetti.described as looking like spaghetti.
Tapeworms can also be vomited up but theseTapeworms can also be vomited up but these
are flat and obviously segmentedare flat and obviously segmented

33. Life cycle pigsLife cycle pigs
 The large roundworm (The large roundworm (Ascaris suumAscaris suum) is found) is found
in the small intestine of pigs and can grow toin the small intestine of pigs and can grow to
400 mm long and 7 mm thick at maturity.400 mm long and 7 mm thick at maturity.
 Heavily infested pigs may have up to 250Heavily infested pigs may have up to 250
worms blocking the small intestines and theworms blocking the small intestines and the
bile duct causing loss of appetite, vomiting andbile duct causing loss of appetite, vomiting and
death. In less extreme cases there is reduceddeath. In less extreme cases there is reduced
appetite, poor feed efficiency and slow growth.appetite, poor feed efficiency and slow growth.

35.  PPiigs 6 to 12 weeks old are the most seriouslygs 6 to 12 weeks old are the most seriously
affected, while mature pigs may carry theaffected, while mature pigs may carry the
worms without ill effect. Growth rate and feedworms without ill effect. Growth rate and feed
efficiency can be depressed by up to 10%.efficiency can be depressed by up to 10%.
 The female roundworm is estimated toThe female roundworm is estimated to
produce more than 300 000 eggs per dayproduce more than 300 000 eggs per day
which are passed in the dung of infected pigs.which are passed in the dung of infected pigs.
The eggs can survive for years in moistThe eggs can survive for years in moist
conditions to infect other pigs.conditions to infect other pigs.

37.  Larvae (immature forms) reach the liver afterLarvae (immature forms) reach the liver after
hatching from eggs in the small intestine and passinghatching from eggs in the small intestine and passing
through the gut wall. Liver damage is seen as whitethrough the gut wall. Liver damage is seen as white
'milk' spots on the surface of the organ. Entering the'milk' spots on the surface of the organ. Entering the
bloodstream, larvae reach the heart and then the lungsbloodstream, larvae reach the heart and then the lungs
where they may cause a low grade pneumonia. Afterwhere they may cause a low grade pneumonia. After
being coughed up and swallowed they mature in thebeing coughed up and swallowed they mature in the
small intestine.small intestine.
 The cycle from egg to egg production is completedThe cycle from egg to egg production is completed
within 2 months. The parasite is confirmed in a herdwithin 2 months. The parasite is confirmed in a herd
by presence of eggs in the faeces and evidence ofby presence of eggs in the faeces and evidence of
liver damage (milk spot) at slaughter.liver damage (milk spot) at slaughter.