Streptococcus bovis Infection - Gordon Chalmers

[Guest CS]

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!

 

Gordon Chalmers