T H E   A W A R D   W I N N I N G   A l l   A M E R I C A N   L O F T

 

 

                 Streptococcus Bovis Infection in Pigeons

 

                         

 

Gordon A Chalmers, DVM

                       Lethbridge, Alberta, Canada

                 E‑mail address:  gachalm@telusplanet.net

 

 

     Streptococcus bovis (now called Streptococcus gallolyticus ) is a bacterial organism that, in the

past has been associated with the udder of cows ‑‑ hence the

species name bovis, in reference to bovine, or more plainly,

cattle.  It is also a common, normal inhabitant of the intestines

of many animals, including pigeons.  In dairy cattle, it is an

organism that is usually a signal or marker whose presence

indicates less than optimum sanitation in the environment of the

udder.  By itself, this organism is usually not important as a

cause of inflammation or infection in the udder of cattle

(although it can cause udder infections), but it does signal to

the dairy operator that sanitation around the udder of his cows

is less than desirable.

     In racing pigeons, however, this organism presents a totally

different picture because it is becoming a threat to both old

birds and youngsters in some lofts in Europe.  It appears that

one or more strains of this organism has adapted to cause severe

disease in pigeons, and in Europe at one point, it ranked second

in importance to Salmonella sp. (paratyphoid) as a cause of

disease in pigeons.  One of the several important features of

Streptococcus bovis is its ability to mimic some of the visible

changes seen in paratyphoid infections in pigeons, namely,

septicaemia (meaning the presence of bacteria multiplying in the

bloodstream), and one of the consequences of septicaemia,

swelling of the joints when these bacteria invade the joints.  As

well, differentiating between infection by Streptococcus bovis

and adenoviral infection is also difficult.  Vomiting, which is

one of the main features of adenoviral infection, has not been

evident in this streptococcal infection.

     In one published study, 20 cases of infection caused by

Streptococcus bovis were found among 293 submissions of pigeons

(mostly racing pigeons) to one laboratory in Europe.  In 17

birds, the major finding was swelling and abscess‑like changes in

the liver (strictly speaking, birds don't produce pus, so it is

not correct to call these changes "abscesses").  Swelling and

abscess‑like changes were also found in the kidneys of 14 birds,

swelling of the spleen of 11 birds, enteritis (inflammation of

the intestines) in three birds, congestion of the lungs and

pneumonia in two birds, degeneration of breast muscles in one

bird, white spots in the heart of one bird, air sac infection in

one bird, and joint infection in one bird.

     When the authors of the report on the European study had

complete background histories on birds submitted for examination,

they found the following information in five cases.  In one case,

10‑14 day‑old youngsters died after 1‑2 days of prostration and

lack of appetite. It was found that only one of the two

youngsters in a pair was affected.  The liver of these birds was

mottled and congested, along with congestion of the kidneys. 

     In another case, breeders housed in a densely‑stocked loft

in which sanitation was poor, lost weight.  New pigeons had been

introduced to the loft on a regular basis.  Liver and spleen of

two birds examined were severely congested.  Inflammation of the

liver and kidneys was also found.

     In a third case, one bird from each of three pairs of

breeders died suddenly in a period of one week, right after their

eggs hatched.  Their youngsters and other breeders remained

healthy.  These birds had been examined for Streptococcus bovis a

few months earlier, and were found to be entirely negative.

However, several new pigeons had been introduced to the loft in

the meantime.  These breeders had a septicaemia, and colonies of

organisms were found distributed to many tissues.

     In a fourth case, one bird had chronic arthritis of the hock

joint and abscess‑like changes in the kidneys after it had

survived an outbreak of paratyphoid, and did not respond to

treatment with Baytril.  (Note this point about Baytril and

Streptococcus bovis!  See later information.)  A pure culture of

Streptococcus bovis was recovered from the liver and hock joint

of this bird.

     In the final case, a bird had died after one day's illness.

Post mortem examination revealed a one‑inch diameter pale, hard

area in the left breast muscle.  Many bacteria typical of

Streptococcus bovis were found in this area.

     Distilled to its essentials, Streptococcus bovis manifests

its presence in pigeons in a number of ways, including invasion

of the bloodstream and massive multiplication and distribution to

a number of tissues and organs (liver, kidney, spleen, muscle,

lung, heart, air sacs, joints), as well as infection of the

intestines and production of diarrhea.

     Experimentally, the same researchers inoculated cultures of

this organism into pigeons, firstly by intravenous injection in

one group, and in a second group, by mouth.  All pigeons injected

intravenously became very ill and developed excess urination,

beginning from the first week of this study.  One young bird

became lame by the 12th day, and at post mortem examination, this

bird plus three others were found to be in poor body condition,

and had enlargement of the liver and spleen.  The affected joint

contained yellow, creamy material. 

     Five other birds also injected intravenously with

Streptococcus bovis were observed for a total of 50 days after

inoculation.  Three of these birds passed a great deal of urine

at intervals, and all of these birds had marked weight loss of

10‑19%.  Streptococcus bovis was not cultured from any tissue

when this group of birds was examined at post mortem on day 50.

     In the group of six birds inoculated with Streptococcus

bovis by mouth, two birds began to pass the organism in droppings

by the third day, and another bird, by the fourth day.  The other

birds in the group did not shed this organism in their droppings.

Two of the three pigeons shedding the organism in droppings were

also found to have it in the throat.  All birds in this group

became negative on culture after one month, and none of them

developed any sign of illness during the experiment.

     The results of these experiments showed that the disease

that occurred in inoculated birds varied considerably in its

expression.  As well, the course of the disease varied from very

acute to chronic.  The results also indicated that the disease is

very difficult to diagnose without a post mortem examination and

a bacterial culture of several tissues.  They also showed that

the signs and changes in this streptococcal disease mimic those

of paratyphoid. 

     Another European study published in 1993 presented

information on antibiotic treatment of infections caused by

Streptococcus bovis in pigeons.  It had been shown in earlier

experiments that this organism was recovered from the intestines

of 40% of healthy pigeons of all ages, and that pigeons that

carry the organism in the intestines usually do not develop this

disease.  It was the opinion of these investigators that some

unknown factor(s) might predispose pigeons to development of

infections in the bloodstream, and as a result, disease.  Signs

of the disease include sudden death in pigeons of all ages,

inability to fly, lameness, emaciation, excess urination, and

green, slimy droppings.

     In the usual course of events in determining the best

product to use in treatment, human and veterinary diagnostic

laboratories run specific tests on bacteria that are cultured

from tissues of diseased humans, birds and animals, to provide

guidance in the choice of antibiotic or other product to use in

treatment.  In this study, cultures of Streptococcus bovis  were

inoculated intravenously into several groups of pigeons.

However, 48 hours before the intravenous injections, each group

of pigeons was given a different, specific antibiotic in the

drinking water, and these treatments continued through until 72

hours after the inoculation. 

     The results indicated that ampicillin and doxycycline

prevented illness in 80% of birds tested, erythromycin in 70% of

birds tested, enrofloxacin (Baytril) in 30% of birds tested, and

trimethoprim in 10% of birds tested.  Obviously, the two poorest

drugs in these tests were Baytril and trimethoprim, so they would

not likely be the first choices for treatment of this disease,

although are very useful in other situations.  The results of

these experiments involving live birds treated with antibiotics

correlated very well with the usual type of antibiotic

sensitivity testing done routinely by many veterinary diagnostic

laboratories.  In such laboratory tests, live birds and animals

are not used, but even so, agreement between the two types of

tests was very good.

     Overall, the authors of this study concluded that, under

field conditions, ampicillin is likely the antibiotic of choice

in the treatment of Streptococcus bovis, since in general, most

species of Streptococcus tend to be highly sensitive to

penicillin and amoxicillin (chemical relatives of ampicillin).

However, Streptococcus bovis seems to have acquired high

resistance to antibiotics such as the tetracyclines (eg.

Aureomycin and Terramycin, for example).  Most strains of this

organism were highly sensitive to erythromycin, but because

strains of lactobacilli living in the crop of pigeons are able to

inactivate erythromycin and spiramycin, the use of erythromycin

in pigeons may be limited.

     A further key finding in the use of antibiotics was that the

much‑touted Baytril was among the poorest products in dealing

with this infection.  Given the widespread use ‑‑ and, I suspect,

overuse and misuse ‑‑ of Baytril, it is reasonable that fanciers

would reach for the Baytril when a streptococcal infection occurs

in their birds, but information from Europe indicates that it is

not the drug of choice in treating this streptococcal infection.

     Because Streptococcus bovis is an organism that can be part

of the normal bacterial population of the intestines of normal

healthy pigeons, the factors that allow it to invade the

bloodstream of pigeons are presently unknown.  Some clues suggest

that such invasion may be related to poor sanitation in pigeon

lofts in which the disease occurs.  Poor sanitation may allow for

a massive buildup of potentially dangerous bacteria, viruses,

etc., and exposure of pigeons to such huge numbers of organisms

can overwhelm their immune systems, and allow disease to occur.

Housing pigeons on wire floors may be a partial answer, because,

according to this study, the lowest prevalence of this disease

occurred in lofts with wire floors.  (Given the various

manifestations of this streptococcal infection, it is also

tempting to wonder about the role of other agents, such as

circovirus for example, which is known to damage the immune

system of pigeons so severely that they become highly susceptible

to many other infections.  Whether the European investigators

looked for this or other intercurrent viral agents can't be

determined from a perusal of their published work.)

     Although certain antibiotics seem to offer good control of

the disease, at least based on current studies, treatment in the

field situations may be somewhat more difficult.  This is because

these infections often have a good start before antibiotics are

used in the first place, and poor sanitation in these lofts may

interfere with treatment.  During outbreaks in Europe, it was

found that excretion of Streptococcus bovis from the intestines

of pigeons resumed once antibiotic treatment stopped ‑‑ which

means that these organisms continued to live in the environment,

ready to cause disease again at a future time.

     It is possible that on a practical level, Streptococcus

bovis will prove to be a difficult bacterial organism to deal

with.  It seems that improved or well‑maintained sanitary

practices in the loft will go a long way toward prevention of

infections, but even so, there is no guarantee that disease

caused by this organism will not occur.  Only time and

investigation will identify a number of the factors that play a

role, not only in the development of this disease, but in methods

of control and prevention.   Whether veterinary diagnostic

laboratories in North America are reporting these infections in

pigeons is unknown at this writing.

     If sudden death or unexplained illness occurs in a loft when

sanitation is not the best, or if new birds have been introduced

prior to the onset of illnesses or death, it is important,

regardless of the cause, to have birds examined by a veterinary

practitioner, especially one who is familiar with pigeons or

exotic birds.  Submission of representative birds by your

veterinarian to a diagnostic laboratory can help immensely in

detecting infectious or other diseases, and defining the precise

cause, as well as providing information on the correct treatment.

This is as true for all infectious diseases as it is for the

disease caused by Streptococcus bovis. 

     As fanciers, we need to be aware of this and other diseases

of pigeons, particularly since so many such diseases can be

imported along with pigeons from all areas of the world.  Given

the brisk world‑wide trade in pigeons today, especially from the

European hotbeds of racing, it seems only inevitable that this

and other important diseases will land on our doorstep ‑‑ and of

course, quite a number have arrived by these means already.

     In summary, it is important to note that infections caused

by Streptococcus bovis in pigeons can mimic those caused by

paratyphoid organisms, possibly E. coli, and in some instances,

could be confused with adenoviral infections.  The key is to have

affected birds examined by post mortem, and to have various

organs cultured to determine the identity of the bacterial agent

causing the problem.  Only in this way can a cause be determined

when losses such as those described earlier occur in a racing

loft.  One last reminder:  Baytril is NOT the drug of choice in

this disease!