Rotavirus involvement in intestinal infections
of poultry and other birds
A. Lublin*, S. Mechani, S. Perk
Division of Avian & Fish Diseases, Kimron Veterinary Institute
POB 12 Bet Dagan 50250, Israel
*lublina@int.gov.il
V. Bumbarov
Division of Virology, Kimron Veterinary Institute
POB 12 Bet Dagan 50250, Israel
Rotavirus. Rotavirus is a double-stranded RNA virus of the Reoviridae family with a
three-layer capsid 70-80 nm in diameter lacking an external envelope. The virus is
one of the causes of enteritis with diarrhea in birds as in mammals but there is no
consensus about cross infection between the two groups. Rotavirus invades the
intestinal mucosal cells especially at the edges of the intestinal villi, and viral
replication causes lysis of the host cells and impairing of absorption. The main
replication site is enterocytes of the small intestines, but also in colon and cecum.
Clinical signs of rotavirus infection include growth retardation, lack of uniformity in
flock, low food conversion, diarrhea, anemia, abnormal feathering and sometimes
bone lesions. Immunosuppression and outbreaks of other intestinal pathogens such as
Clostridium or coccidia, is common in rotavirus infection. The virus is excreted in
feces in high numbers, and can be transmitted directly and indirectly. The most
important portal of entry is by ingestion. Most of the information is derived from
poultry and less information is available for pet birds.
Rotavirus in poultry. In broilers we found association between rotavirus infection and
malabsorption syndrome, that according various researchers, reovirus either rotavirus,
is its main etiology. The main pathological lesions of the syndrome consist of whitecolored or transparent intestinal walls, enlarged gall bladder, sometimes
proventriculitis, pancreatic atrophy, degeneration of bursa of Fabricius and rickets.
Serological survey for reovirus in stunted flocks resulted in absence of titers in an
experimental model in which infected intestinal contents from retarded birds were
inoculated into specific pathogen free 1–day-old chicks and follow-up for antibody
titers in affected birds (as most of the inoculated chicks became). In contrast, in 8 out
of 18 flocks (mostly broilers) with signs that may indicate rotavirus, a group Arotavirus antigen – major inner capsid protein VP6, could be detected by ELISA and
by immunohistochemistry, with significant correlation between the two diagnostic
methods (chisquare coefficient 4.04, P<0.05). Sixteen tested flocks out of 21 received
the same result in both methods. In few of the cases the virus was diagnosed also by
electron microscopy using a negative staining technique, and by immuno-electron
microscopy with rotavirus antiserum. Diagnosis of the virus by immunofluorescence
was also tested but the results were not satisfactory. One of the advantages in using
immunohistochemistry is the ability to locate the virus in tissue (as red color appears
at the sites of antigen localization).
Rotavirus was diagnosed especially in intestinal mucosal cells and in a lesser extent in
the inner connective tissue of the mucosa i.e. lamina propria. The virus was observed
also inside intestinal contents making the excreted feces in the intestinal lumen as the
route of virus spreading.
The clinical disease (retarded growth with or without diarrhea) could be reproduced in
12 inoculation experiments with filtered intestinal contents after their administration
directly into crop of specific pathogen free 1-day-old chicks. The syndrome could not
be reproduced in chicks older than 2 days. Inoculation of turkey poults could not
reproduce the disease. Thus, sensitivity to rotavirus infection is limited to chicks up to
age of 1-2 days.
Testing different segments of intestines for rotavirus infection revealed the highest
rate of infection in cecum, in 42% of the cases, in comparison to 15% of cases in
duodenum and 29% in jejunum-ileum.
Rotavirus was detected by ELISA also in poultry manures, in averagely 37% of the
manures. Virus prevalence was relatively high in turkey manures (about 40%), but
was found also in manures from broilers, breeders, layers, pullets and “organic
chickens”. The high prevalence in manures is probably due to its high resistance in
the environment and its accumulation in manure.
Rotavirus in pet birds. In pet birds rotavirus is one of the causes of gut dilatation and
impaired food absorption, widespread especially in pigeons and lovebirds. Watery
diarrhea may occur in infected pigeons. Some of the strains do not cause clinical
symptoms in carrier birds.
Rotavirus is less familiar in pet birds than in domesticated birds. In a survey in our
laboratory, the virus was diagnosed by ELISA only in 3 birds out of 18 suspected
according to clinical and pathological signs: two African gray parrots (Psittacus
erithacus) with pathological presentation of proventricular dilatation disease (PDD)
and a ring-necked parakeet (Psittacula krameri) from a flock with respiratory
disturbances and mortality while necropsy findings in this case included diarrhea,
proventricular dilatation and undigested food as in other cases. In addition, rotavirus
was detected in two birds without clinical suspicion (African gray parrot, cockatoo).
It seems that rotavirus is more abundant in stunted poultry than in pet birds with
similar signs.