Ruminant

1
Ruminant Liver Parasites
2
Condemned Liver
Annual condemnation of livers of 3-4 of US
cattle (25 Louisiana) at 3-5 each due to
parasites.

• Adult-Biliary hyperplasia, dilatation, fibrosis,
  calcification
• Migration-Diffuse fibrosis, shrunken ventral lobe

3
Distribution of Fasciola in the USA
Determinants Neutral, well buffered soils
(Ca) in alluvial river basins, prairies and
coastal marshes that support Lymnaea intermediate
hosts, a mud snail that occurs in
well-oxygenated shallow water bodies that
periodically freshen with rains. In western
states, habitats are typically springs, sloughs
or seeps in coastal and mountainous zones.
4
Life Cycle
50o F (10o C) is the base temperature required
for progression of both the Lymnaea life cycle
and the development of free living stages in the
environment. Optimum development occurs at 18o C
10 days at 25 C 115 days at 10 C
Encyst in hours
Total time free living stages 2 to 5
months
Asexual reproduction? sporocysts, rediae takes 42
days at 25 C, 115 days at 15 C
Lives 24 hr
5
Metacercariae excyst in the duodenum and
penetrate via the peritoneum into the liver
parenchyma by 4-5 days. Migrating flukes leave
necrotic tracts in their wake, enter bile ducts
after 6-8 weeks and grow rapidly to adult egg
shedding flukes by 8-10 weeks. Maximum egg
shedding is at 14-20 weeks. Fasciola is most
pathogenic at entry to bile ducts, and in the
rapid growth and early egg shedding phase lt6
months after major infection.
6
Hosts

• Cattle Partial immunity builds, self-cure at
  5-8 months after major infection, most gone
  within 1 year.
• Sheep and goats Little immunity, flukes live up
  to 10 years
• Rabbit, swine, other incidental hosts are
  potential reservoirs
• Zoonotic human infection via watercress,
  vegetables is a major problem in the altiplano of
  the Andes, Egypt, Iran, sporadic elsewhere

7
SnailHabitat
Typical habitat in alluvial Red River Basin.
Habitats are shallow depressions (eg.
imperfections in ditch and crown drainage
systems seen here) that stay wet half the year
and freshen with each rain. Lymnaeid snail hosts
are found on mud at the edge of habitats. Rain
stimulates shedding of cercariae by snails, a
dispersal adaptation that helps spread infection
to a larger area of the pasture. Most infections
are focal, in and around snail habitats.
8
Hoofprint with Lymnaea
Snails grow to about 1cm in length
9
Eggs persist in dung pat reservoirs on pasture,
must be washed free of feces into water phase to
develop further into miracidia.
10
Fasciola egg
Eggs are large, operculated and golden in color
Fasciola is diagnosed by fecal sedimentation
examination
11
Miracidia are stimulated to hatch from eggs by
light after at least 10 days development
12
Lymnaeid snails have a dextral spiral shell whorl
(right-handed) and cat ear antennae
13
Asexual Multiplication in snail hosts result in
a sporocyst and two rediae generations. Rediae
produce cercariae. One miracidium can lead to
several hundred cercariae
14
Metacercariae have a resistant 4-layer cyst wall
and survive months in wet, cold conditions. A 2
week sustained summer drought kills metacercariae
and forces estivation of snail populations, thus
ending the transmission season
15
Pathogenesis
Fluke with Spines of flukes in bile ducts erode
proliferated epithelium and consume blood and
exudate. Proline, a by-product of the incomplete
metabolism of Fasciola, rises to 1000 times
normal. Proline excess has been shown to lead
to bile duct fibrosis and depression anemia
experimentally. Fasciola consumes only 0.2 ml
blood/fluke/day, not enough for the anemia,
hypoproteinemia seen with heavy fluke infections.
16
Heavily Parasitized Heifer Subacute clinical
infections are seldom seen in cattle, associated
with burdens of gt200 flukes. Chronic
sub-clinical disease is typical. Most fluke
effects occur 6-20 weeks after heavy exposure
(after entry to bile ducts), then lessen. An
8-28 reduction in rate of gain has been reported
in feeder calves infected with 40-140 flukes.
Minor effects with lt10 flukes.
17
Sheep with bottle jaw Sheep and Goats High
mortality outbreaks can occur. Acute disease
occurs at bile duct entry of massive (gt5000
metacercariae) numbers of flukes. Sub-acute and
chronic clinical disease is due to burdens of
gt800 and gt200 adults in bile ducts, respectively.
18
Liver infarct, Bacillary Hemoglobinuria
Bacillary hemoglobinuria is predisposed by fluke
migration anaerobic tracts. In some geographic
areas of the west, vaccination of cattle must be
given each 6 months where soils favor persistence
of Clostridium hemolyticum. Cl. Novyi causes
Black disease in sheep, and rarely cattle, with
multifocal lesions. Anaerobic bacteria
proliferate in necrotic tracts and produce potent
exotoxins and acute death.
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Control programs
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(No Transcript)
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Seasonal Transmission Diagram of the Gulf Coast
Region based on 5 years experimental data Late
winter, spring transmission
22
100-fold annual variation in fluke transmission
and risk of economic losses at a farm near
Alexandria, LA, with corresponding spring and
fall climate forecast indices.
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Climate Forecasts
INPUT - Maximum/Minimum Temperatures C
- Precipitation CALCULATIONS - Growing
degree days (Base 10o C) and soil moisture water
budget. - Accumulate (add) GDD if water in
top 1 of soil - Surplus water
(run-off) times GDD on rain days ACCUMULATES
DAILY LIFE CYCLE INDEX Risk increases
exponentially with index due to the multiplier
effect of the asexual reproduction phase in
snail hosts. This makes possible the well known
explosive nature of fluke outbreaks.
24
Fasciola climate forecast regional risk index map
for Louisiana and Texas in an average year (based
on 30 year average climate data)
25
Individual farm risk is related to the area
occupied by snail habitat and stocking rate.
Farms with over 5 habitat area are very high
risk premises. This is a low-lying high risk
cow-calf operation in coastal Louisiana.
26
Individual farm risk also can vary by 100 fold in
the same area, based on drainage characteristics
of soil texture classes (eg. sand loam, loam,
clay loam, clay, hydric clay). White lines
indicate farm boundaries overlayed on USDA soil
type map.
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Treatment
__________________________________________________
___ Bile duct
Bile duct Parenchyma
Drug
Adults Immature Migratory
Hexachloroethane 90 ?
- Albendazole 10mg/kg 75-90 33
- Clorsulon 7mg/kg gt99
96 - in Ivomec 2mg/kg
gt90 gt70 - Triclabendazole
gt99 gt99 gt90
(10mg/kg, available worldwide, not
USA) _____________________________________________
________ Removed from market as a carcinogen in
1985
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Southern USA pattern
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Western US Pattern
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Rationale of treatment recommendations

• Treat in each region two months after
  transmission season ends to allow flukes to
  become adult and susceptible to available drugs,
  but while still in maximum pathogenic phase
• The end of season can be determined by producers
  when habitats dry up (eg. when springs, seeps,
  sloughs dry up in the west) for gt2 weeks in
  summer-fall or when sustained periods of winter
  cold lt10 C begin.

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Herd egg count monitoring
Interpretation Prevalence Mean
EP2G Low burden lt 25
lt 1 (No economic losses) Moderate
Burden 25-75
1-3 (Economic Loss Possible) Heavy Burden
75-90 3-10 (Economic loss
probable) Economical gt90
gt10
________________________________________________
-Fasciola must be differentiated from
Paramphistomum, a non- pathogenic rumen fluke
that is smaller, greyish in color -Examine 10
cows
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Herd sampling and examination
Several immunodiagnositic tests have been
developed for Fasciola, including a serum ELISA
and one based on detection of coproantigen in
feces. Some are used in Europe, but are not yet
commercially accepted in the USA.
33
Fasciola gigantica vs F hepatica
F. gigantica is the tropical-sub-tropical
counterpart of F. hepatica. It is 2-3 times
larger, somewhat more pathogenic, and has a
longer prepatent period (10-12 weeks). Lymnaeid
vector spp are more aquatic, inhabiting
permanent bodies of water, irrigation canals and
seasonal flood areas.
34
Fascioloides magna
Deer are normal hosts, cattle and sheep
incidental hosts
35
Fascioloides magna in infected deer liver. Note
the mild inflammatory response of deer, the
normal host.
Note the large size of F. magna and the black
lymph nodes and streaks of pigment in this cattle
liver due to regurgitated fluke ingesta.
36
Deer liver heavily infected with F magna. Heavy
burdens are well tolerated by deer and
pathological reaction is mild due to a well
adapted host-parasite relationship. The life
cycle is similar to F hepatica, but has a wider
geographic distribution associated with the wider
variety of snail hosts, some in more aquatic
habitats. Flukes are found in parenchyma cysts
with a fistulous communication to bile ducts for
escape of eggs.
37
Cattle liver with F magna. Note the more intense
pathological reaction, with calcification and
dark pigmentation caused by flukes in liver
parenchyma cysts. Diagnosis is made in cattle
mainly at slaughter inspection because
communication of cysts with the bile ducts is
walled off by inflammation, preventing egg
shedding. Little economic damage is associated
with F magna in cattle, except in some parts of
the country with heavy infections acquired on
ranges shared with abundant deer (eg Texas
hunting clubs). In LA, 2 of livers condemned
have F magna.
38
In sheep, F magna is not walled off and flukes
continue to migrate with ultimate destruction of
the liver parenchyma. One or two flukes can kill
sheep and this parasites effectively limits sheep
production in parts of the great lakes region and
other areas where ranges must be shared with deer
populations.
39
Paramphistomum Rumen fluke in situ among rumen
papillae. Note the conical shape and attachment
by a posterior sucker, an adaptation of the
ventral sucker
40
The posterior sucker of a paramphistome attached
to rumen epithelium. The rumen fluke is not
considered to be pathogenic in the USA, although
massive infection (gt30,000) by tropical species
may cause severe, fatal disease due to duodenitis
caused by the larva migration phase of the life
cycle in the duodenum mucosa. The life cycle and
transmission on forage is similar to F hepatica.
41
Paramphistome eggs are greyish, more pointed at
the operculum end and slightly smaller, features
which allow differentiation from Fasciola at
fecal sedimentation examination. Paramphistomes
are often found in the same herds as Fasciola and
in the Southeast are transmitted by the same
snail. Since they are not affected by available
flukecides, they can be counted and used as a
surrogate indicator of how severe Fasciola would
be without benefit of control programs.
42
Dicrocoelium Adult fluke
Dicrocoelium eggs are small in size and contain a
fully developed miracidium
43
Dicrocoelium land snail host shedding eggs in
slime balls
Black ant second intermediate host consuming
snail slime containing cercariae
44
Dicrocoelium metacercariae encyst in brain
tissues of ants, causing acrophilia a
behavioral disturbance that induces them to climb
high on vegetation, clamp down with pincers
during cool of night, and so become more
available to early grazing animals.
Distribution is limited to central New York and
areas of Pennsylvania, New England , Quebec,
British Columbia by the distribution of the snail
and ant hosts. It is common in Europe and Asia.
Crazy ant on flower.
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Dicrocoelium

• Final host range is wide including sheep, cattle,
  horses, pigs, man, deer, woodchucks.
• Excyst in the duodenum, migrate directly up the
  bile ducts and are usually well tolerated.
  Several thousand cause clinical signs.
• Treatment and control Thiabendazole and
  Fenbendazole are effective. Other measures are
  to eliminate snail habitat (remove old boards,
  debris refuges of snails) and introduction of
  poultry or ducks as predators of snails.