Possible typhus-group infection in New York State: presentation of four suspect cases

The neglected saliva: medically important toxins in the saliva of human lice

Although there has been a great deal of research effort within the last two decades on identifying the active components of the saliva of blood-sucking ticks, mosquitoes, biting flies, fleas and bugs, essentially neglected have been the human lice. Despite initial reports in the early part of this century suggestive of vasodilatory, anticoagulant and immunosuppressive properties of the saliva, for the next 50 years there were no biochemical studies on the active principles. Very recently, anatomical and biochemical studies have begun to characterize the bioactive molecules in lice saliva. The louse stocks a salivary vasodilator in excess over what is needed for a single bite, and injects similar amounts at each successive bite. The vasodilator in lice saliva appears to have different pharmacological properties than peroxidative, oxidative and maxidilan types of vasodilators reported from other blood-sucking insects. Possible anticoagulant activities have also been characterized. This belated, but welcome, interest comes at a time of resurgence of lice-born disease in certain parts of Africa, and of resistance to chemical control in Europe and North America.

Identification of a novel rickettsial infection in a patient diagnosed with murine typhus

Identification of ELB agent-infected fleas and rodents within several foci of murine typhus in the United States has prompted a retrospective investigation for this agent among human murine typhus patients. This agent is a recently described rickettsia which is indistinguishable from Rickettsia typhi with currently available serologic reagents. Molecular analysis of the 17-kDa antigen gene and the citrate synthase gene has discriminated this bacterium from other typhus group and spotted fever group rickettsiae. Current sequencing of its 16S ribosomal DNA gene indicates a homology of 98.5% with R. typhi and 99.5% with R. rickettsii. Through a combination of restriction fragment length polymorphism and Southern hybridization analysis of rickettsia-specific PCR products, one of five tested patient blood samples was shown to be infected with ELB while R. typhi infections were confirmed in the remaining samples. This is the first reported observation of a human infection by the ELB agent and underscores the utility of PCR-facilitated diagnosis and discrimination of these closely related rickettsial infections.