Following the initial period of fever there is usually a short afebrile interval of a few days to be succeeded by a second, third or many of these febrile waves, thereby making one of the names, undulant fever, appropriate. Anaemia becomes marked and cardiac weakness, as shown by palpitation and rapid, irregular pulse, apparent.
The symptoms which aid us most in diagnosis are joint manifestations and neuralgic pains. These may come on quite early in the course of the disease or be delayed until succeeding febrile waves set in. Swelling and pain, but without redness, of a single joint may come on rather suddenly, to have the acute symptoms subside in a few hours and to be entirely normal in three or four days.
Pains in the sacro-iliac region or pains resembling those of hypertrophic arthritis of the spine may be noted.
It is however the peripheral nerves, even more than the joints, for which the toxic effects of M. melitensis show a preference. The sciatic nerve seems to be most often involved and sciatica may set in suddenly and acutely, to pass off in two or three days, leaving a soreness over the course of the nerve and a tendency to recurrence. Orchitis may occasionally set in. There is usually albuminuria.
Insomnia is usually quite a prominent feature of the disease and there is a great tendency for nervous prostration to develop.
The usual course of the disease runs for three or four months but may last almost a year.
Other Clinical Types.—(1) The Malignant Form.—In such cases instead of the insidious onset we have the characteristics of a severe acute infection with high temperature from the beginning, ranging from 103° to 105°F. Such cases may show vomiting and early diarrhoea. This is followed by a typhoid state with cardiac manifestations in the way of irregularity of the pulse. An ordinary type of case may assume this malignant form and such cases may develop a broncho-pneumonia.
(2) The Intermittent Form of Hughes.—Here we have a type of case similar to the typical one but less severe. It is a subacute form which from time to time shows an intermitting fever. These cases may fail to show evidence of serious illness and the patient may continue his work although noting a progressive deterioration of health. Some very mild cases which only rarely show slight fever of a few days’ duration have been reported as ambulatory cases.
(3) The Disease in Infants.—Di Cristina and Maggiore have described various forms of the disease as observed in infants in Palermo. They note a hyperpyrexial type and an undulant type. A type with anaemia and marked cachexia is very severe. Another form shows cyanosis, irregular pulse and irregular respiration with marked sweats. Again the symptoms may be those of a cerebro-spinal meningitis.