Blue Eye Disease Porcine Rubulavirus
Porcine Importance
Porcine rubulavirus infection or “blue eye” disease is an emerging disease first
Rubulavirus seen in La Piedad, Michoacan, Mexico and the neighboring states of Jalisco and
Infection Guanajuato in 1980. It is characterized by encephalitis and respiratory disease in
piglets, reproductive failure in adult pigs, and occasional corneal opacity in all ages.
Etiology
La-Piedad-Michoacan
Paramyxovirus Infection,
Blue eye disease is caused by the porcine rubulavirus, which is also called the
La-Piedad-Michoacan paramyxovirus (LPMV). This virus, which was first isolated in
Blue Eye Disease
Mexico in the early 1980s, belongs to the genus Rubulavirus and family
Paramyxoviridae. Only one serotype is known.
Last Updated: March 28, 2006
Species affected
Pigs are the only known host species.
Geographic distribution
Blue eye disease has been reported only from Mexico; however, closely related
paramyxoviruses of pigs have been found in other countries including Australia,
Canada, Japan, and Israel.
Transmission
Infections seem to be spread mainly by the respiratory route. A large amount of
infectious virus has also been found in the urine. Vertical transmission occurs in utero.
Incubation period
In experimental studies, symptoms appeared 3 to 5 days after intranasal
inoculation of piglets.
Clinical signs
In 2 to 21 day old suckling pigs, blue eye disease is characterized by encephalitis,
pneumonia, and corneal opacity. Typically, the disease begins with the sudden onset
of fever, arched back, and prostration or depression. These symptoms are followed by
progressive neurologic disease with weakness, ataxia, muscle tremors, abnormal
posture, and rigidity mainly in the hind legs. Some piglets are hyperexcitable; they
may squeal and make paddling movements when they are handled. Approximately 1-
10% of the piglets develop unilateral or bilateral corneal opacity, which usually
regresses spontaneously. Other symptoms may include conjunctivitis, apparent
blindness, nystagmus, constipation, and diarrhea. Affected piglets often die. The first
piglets usually die within 48 hours of the onset of clinical signs; later, deaths are seen
after 4 to 6 days of illness.
Weaned pigs more than 30 days old usually have transient, moderate symptoms
that may include anorexia, fever, coughing, sneezing, and occasional corneal opacity.
Neurologic signs are rare in this age group, but occasional depression, ataxia, circling
or swaying of the head may be seen. On some poorly managed farms, a syndrome
consisting of severe neurologic signs with a 20% mortality rate has been reported in
15-45 kg fattening pigs. On these farms, as many as 30% of the pigs may also develop
corneal opacity.
Non-fatal reproductive failure is seen in older pigs. The symptoms include
decreased conception rates, abortions, increased stillbirths and mummified fetuses in
sows, and epididymitis, orchitis, and reduced semen quality in boars. Some animals
may also have corneal opacity or mild anorexia.
Post mortem lesions
The typical lesions in suckling pigs are interstitial pneumonia and non-
suppurative encephalomyelitis. Gross lesions may include signs of mild pneumonia
(particularly at the ventral tips of the cranial lung lobes), congestion in the brain, and
conjunctivitis and chemosis in the eye. The stomach may be mildly distended with
milk, and the urinary bladder with urine. The peritoneal cavity sometimes contains a
small amount of fluid with fibrin. The histopathologic lesions includes non-suppurative
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Porcine Rubulavirus Infection
encephalomyelitis; the gray matter of the thalamus, mid-
Diagnosis
brain, and cerebral cortex is most often affected. The
Clinical
lungs may contain scattered areas of interstitial
pneumonia, with thickened septae and a mononuclear cell
Porcine rubulavirus infection should be suspected in
infiltrate. Mild tonsilitis has also been reported.
an outbreak characterized by neurologic and respiratory
disease in young piglets, reproductive failure in adult
The main necropsy lesion in experimentally infected
pigs, and corneal opacity in all ages.
boars is severe epididymo-orchitis. The testes may be
atrophied. Histopathologic changes in the epididymitis
Differential diagnosis
may include spermatic granulomas and vacuolar
The differential diagnosis includes hemagglutinating
degeneration of the ductular epithelium, associated with
encephalomyelitis virus infection and pseudorabies.
mononuclear cell infiltrates and interstitial fibroplasia. In
the testes, degeneration of the seminiferous tubules and
Laboratory tests
interstitial mononuclear cell infiltrates may be seen.
Serologic tests include hemagglutination inhibition,
Lesions reported in experimentally infected gilts
virus neutralization, indirect immunofluorescence, and
include focal congestion and hemorrhages in the placenta
enzyme-linked immunosorbent (ELISA) assays. All of
and endometrium. The fetuses may be dehydrated or
the serologic tests detect seroconversion by the 8th day
mummified, or smaller than normal with dermal
after infection.
ecchymoses. Abnormal fetuses are interspersed randomly
The porcine rubulavirus can be isolated in pig kidney
with normal fetuses.
cell line (PK-15) cultures or chick embryos. Other pig cell
Corneal opacity, characterized by anterior uveitis and
lines and primary cultures, as well as baby hamster kidney
corneal edema, may be present in pigs of any age.
cells (BHK 21) and Vero cell lines, are also susceptible. A
rapid diagnostic test, which uses immunostaining to detect
Morbidity and Mortality
viral antigens in impression smears, is also available.
Outbreaks of blue eye disease can be seen throughout
Samples to collect
the year, but they are most common from April to July.
Before collecting or sending any samples from
Most outbreaks seem to be self-limiting. The mortality
animals with a suspected foreign animal disease, the
rate usually rises and falls within 2 to 9 weeks. Once the
proper authorities should be contacted. Samples should
epidemic has ended, no more cases occur unless
only be sent under secure conditions and to authorized
susceptible pigs are introduced to the farm.
laboratories to prevent the spread of the disease.
In commercial breeding operations, the disease is
Serum should be collected for serology. In piglets,
usually noticed first in the farrowing unit, where large
the porcine rubulavirus can be recovered consistently
numbers of young piglets may die from encephalitis.
from the brain and tonsil, and sometimes from the lung,
Typically, 20-60% of the litters are affected. The overall
blood, spleen, liver, kidney, retropharyngeal lymph nodes,
morbidity rate in piglets is 20% to 50% and the mortality
and nasal turbinates. It has also been found in various
rate is approximately 90%; however, the severity of the
tissues of experimentally infected gilts including the lung,
symptoms varies with the age of the animals. Although
tonsils, ovary, placenta, uterus, and lymph nodes. The
severe disease can occur in piglets as old as 21 days,
rapid immunostaining test uses lung, midbrain, or
animals younger than 15 days are most susceptible. In one
olfactory bulb tissue samples.
experiment, 3-day old piglets were all dead or dying
within a week of inoculation, but only 30% of 17-day old
Recommended actions if porcine
piglets became ill.
rubulavirus infection is suspected
In older animals, the virus seems to be cleared by the
immune system. On most farms, the morbidity rate in
Notification of authorities
weaned young pigs (more than 30 days old) is
Porcine rubulavirus infection must be reported
approximately 1% to 4%. The mortality rate in this group
immediately to state or federal authorities upon diagnosis
is usually low. However, on some poorly managed farms,
or suspicion of the disease.
severe neurologic signs with a 20% mortality rate have
Quarantine and disinfection
been reported in 15-45 kg fattening pigs. In adults, the
only symptoms are non-fatal reproductive signs and
The porcine rubulavirus is contagious, and quarantine
occasional corneal opacity. A decrease in the conception
is necessary. Its disinfectant susceptibility has not been
rate usually persists for 6 to 8 months.
published; however, the related Newcastle disease virus,
which also belongs to the genus Rubulavirus, is
Persistent infections may be possible. Viral RNA has
inactivated by formalin, phenol, or acid pH.
been found in pig tissues up to a year after infection, but it
is not known whether the virus multiplies or is excreted.
Public Health
Human infections have not been reported.
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Porcine Rubulavirus Infection
Internet Resources
World Organization for Animal Health (OIE)
http://www.oie.int
References
Allan GM, McNeilly F, Walker I, Linne T, Moreno-Lopez J,
Hernandez P, Kennedy S, Carroll BP, Herron B, Foster
JC, Adair B. A sequential study of experimental porcine
paramyxovirus (LPMV) infection of pigs:
immunostaining of cryostat sections and virus isolation. J
Vet Diagn Invest. 1996 Oct;8(4):405-413.
Department of Agriculture, Fisheries and Forestry [DAFF],
Government of Australia. Generic import risk analysis
(IRA) for uncooked pig meat [monograph online]. Issues
Paper. DAFF; 2001 Jan. Available at:
http://www.affa.gov.au/corporate_docs/publications/
word/market_access/biosecurity/animal/2001/2001-
02a.doc. Accessed 12 Dec 2005.
Hernandez-Jauregui P, Ramirez Mendoza H, Mercado
Garcia C, Moreno-Lopez J, Kennedy S. Experimental
porcine rubulavirus (La Piedad-Michoacan virus)
infection in pregnant gilts. J Comp Pathol. 2004
Jan;130(1):1-6.
McNeilly F, Walker I, Allan GM, Foster JC, Linne T, Merza
M, Hernandez P, Kennedy S, Adair B. A comparative
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techniques for the diagnosis of La Piedad Michoacan
paramyxovirus (LPMV) infection in pigs. J Vet Diagn
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Development of a blocking ELISA for screening
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Ramirez-Mendoza H, Hernandez-Jauregui P, Reyes-Leyva J,
Zenteno E, Moreno-Lopez J, Kennedy S. Lesions in the
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Stephan HA, Gay GM, Ramirez TC Encephalomyelitis,
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1988 Jan 2;122(1):6-10.
Wiman AC, Hjertner B, Linne T, Herron B, Allan G,
McNeilly F, Adair B, Moreno-Lopez J, Berg M. Porcine
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Neurovirol. 1998 Oct;4(5):545-552.
World Organization for Animal Health [OIE]. Animal
diseases data [online]. Newcastle disease. Available at:
http://www.oie.int/eng/maladies/fiches/a_A160.htm.
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