Part VIII.
1. Cross-immunity experiments in the guinea-pig, rabbit and monkey were carried out with the viruses of the tsutsugamushi disease (including rural typhus) and the urban typhus of Malaya; they showed that immunogenically the two viruses are distinct.
2. The characteristics of setiology, epidemiology, serology and experimental infections are compared, and the conclusion drawn that the two diseases belong to entirely separate groups of rickettsial disease.
Part IX.
1. Cross-immunity experiments in the guinea-pig and rabbit were carried out with the viruses of Rocky Mountain spotted fever, tsutsugamushi (including rural typhus) and urban typhus. They showed that, immunologically, tsutsugamushi
and spotted fever are entirely distinct; whereas urban typhus and spotted fever, though more distinct than alike immunologically, do possess a minor degree of reciprocal cross-immunity.
2. Spotted-fever vaccine was found to have no protective value against the viruses of tsutsugamushi and urban typhus.
Fifteen (15) guinea pigs were experimentally infected with Leptospira icterohemorrhagiae serovar Lai strain
Langkawi, a new strain that was isolated from a human leptospirosis patient. Hematoxylin and Eosin ((H&E) staining
showed haemorrhages, congestion and oedema in all internal organs examined (lungs, liver, spleen and kidneys) with
inflammatory cell infiltration characterized by neutrophils, lymphocytes and macrophages. Hydropic degeneration and
cell necrosis were also common in our findings. Leptospires were detected starting Day 2 p.i by silver staining and
Transmission Electron Microscopy (TEM). Rise in antibody titres started on Day 5 p.i and leptospiral DNA was
detected beginning Day 3 in the kidneys and Day 5 in the liver by Polymerase Chain Reaction (PCR) assay. The
findings illustrated the pathogenesis of leptospirosis in guinea pigs which disclosed them as a suitable animal model for
demonstration of clinical symptoms of leptospirosis and pathological changes after being infected with Leptospira
icterohaemorrhagiae serovar Lai strain Langkawi, particularly pulmonary haemorrhages, a leading cause of mortality
in human leptospirosis.
The safety of bacterial cells of Clostridium bifermentans serovar malaysia, which is highly toxic to mosquito larvae, was tested on mice, guinea pigs, rabbits, and goldfish. Inoculations of at least 1 x 10(8) cells per animal by routes recommended by World Health Organization (subcutaneous, percutaneous, inhalation, force-feeding, intraperitoneal, intravenous) and tests of subacute toxicity, anaphylactic shock, persistence in heart blood, and virulence by successive passages, were performed on mice, guinea pigs, or both. Growth was monitored for 1 mo before necropsy. Ocular irritation and skin scarification were tested with rabbits. C. bifermentans serovar malaysia did not induce any mortality or abnormal reactions in mammals at a dose 1,000 times higher than the level established by W.H.O. for the demonstration of safety. Bacterial cells are not toxic to goldfish at a dose 1,000 times higher than the LD50 for the target-mosquito larvae. We conclude that C. bifermentans serovar malaysia bacterial cells are safe for laboratory mammals and goldfish.