As you may have guessed from the quote marks, "lockjaw" is not the scientific name of this serious malady affecting cockatiels (and other birds) while being handfed; rather, it is a description of the main symptom. When chicks become sick with this problem, you probably won't notice any other sign of illness until, one day, your baby's beak won't open. You might also notice that the eyes, or one eye, look swollen and protruding. At first, you think the chick, which might be pretty close to weaning, isn't hungry – that is, until you turn to feed another and the one that wouldn't open it's mouth starts begging piteously. The outlook for chicks affected with this malady, which is really Temperomandibulitis (infection/inflammation of the temperomandibular joint of the jaw) isn't good but they can recover if you can find a way to feed them despite the fact that they can't open their beaks and if nothing else goes wrong. The thing that most often carries my chicks off when they have this is that they regurgitate and then choke because they can't open their beaks to rid themselves of it.
Many people immediately think "Bordetella" when this problem comes up. Although that particular organism can cause these symptoms (plus a runny discharge from the nares), it is not the only causative agent. This is good, as successful treatment and recovery is doubtful when "Bordetella" is the bacteria causing the problem, perhaps because this particular organism does not respond very well to antibiotic therapy.
I have had about six instances of this problem, in which one up to five out of a group of up to ten cockatiels gets the lockjaw symptom and some or all of the other symptoms. Although I have had necropsies done each time, including once sacrificing a live bird that had the disease, Bordetella has never been found in the chicks I had that died of this disease. In fact, although inflammation of the TMJ was found in every case, no particular bacteria has been isolated as causing the problem. . The necropsies did note the presence of bacteria that would have normally been present in the birds' mouths.
Dr. Cheryl Greenacre at the University of Georgia's Veterinary school has written on this subject "An outbreak of temperomandibular rigidity was experienced by a number of 3 – 4 week old handfed cockatiels in an aviary. The affected birds were thin, had ravenous appetites and various degrees of TM joint rigidity….. Entercococcus bacteria were cultured from the TM joint of the affected birds…It was theorized that the practice of feeding with a sharp curved-tip syringe induced trauma to the oropharynx allowing entrance of the Enterococcus bacteria into the TM joint…These cases responded well to antibiotic therapy based on culture and sensitivity results, however decreased joint movement persisted after therapy. This outbreak demonstrates that several different organisms, each of which carries a different prognosis, can cause TM joint rigidity. It also demonstrates the trauma that can be caused by improper hand feeding techniques in juvenile birds.
"So, if your cockatiels, while handfeeding, get the locked jaw symptom, just pray that it is caused by some other organism than Bordetella, as there is a small chance of recovery from other causative agents. I must sadly admit, though, that the chances for recovery are not high. Out of about twenty cases over the past three years, I have two birds that survived the two months of locked jaw and thereafter. One of those recovered from all its symptoms eats well on its own and is now six months old and living in our outside aviary, where he is thriving in our winter weather with no heat! This is a strong indication, it seems to me, that the bird is fully recovered and its immune system is strong. I held on the other bird, after seemingly full recovery, for two additional months, and then sold it as a pet. It was later reported to me that the bird died after being given as a gift for Christmas. Unfortunately, no necropsy was done. I will note that I did refund this customer's purchase price. Although I had no way to know if the locked jaw episode had contributed to the early death of this bird. I also could not say for sure that it had not.
I have noticed that these cases have occurred with other species besides cockatiels (one Indian Ringneck) and have occurred with parent-raised chicks. It also happens when chicks are fed with other types of feeding utensils (other than the curved-tip syringe mentioned by Dr. Greenacre). With the chicks I've handfed that got this disease, the only constant was my way of handling the chicks during feeding. I finally reached the conclusion that my practice of placing my thumb and forefinger on each side of the chicks'' head in order to hold it steady is the factor that causes damage to the TM joint and allows the entry of bacteria. In fact, my observations lead me to believe that some sort of trauma was present in every case. Needless to say, I am paying more attention and consciously handling the chicks" heads more gently. Since I started being more aware of my methods, I haven't had new cases but I also haven't fed many chicks since then. With breeding season starting up again, I will now get an opportunity to check my theory!
I've also had cases where parent fed birds developed this problem. I wound up pulling and treating (and losing) 3 out of 4 babies from a clutch, but the fourth remained perfectly normal.
I do want to stress here that I am not a veterinarian and this article is not intended to be a substitute for veterinary advice when this problem is encountered. My intent is only to share my experiences and observations with this malady in the hope that, if you ever encounter the problem, you will not be absolutely mystified, as I was the first time.