1. Focus on pathogens: Babesia microti Facts / life-cycle: B. microti, which causes babesiosis, is the only member of the genus that infects man. This organism is similar to the bacterium causing Lyme disease in that both are endemic to the NE US (especially CN), both use the white footed mouse as resevoir (IH) and both are transmitted by deer tick bite (40% of which are coinfected). However, B. microti is much more likely to be sub-clinical. cont 

2. Facts / life-cycle continued Although the life-cycle is complex, that involving human pathology is not. Trophs (comparable to malarial sporozoites) are introduced via tick bite, migrate to RBCs, develop to the ring form, and divide asexually to form merozoites which can follow an auto-infective cycle parasitizing additionaly RBCs. Either form may also be introduced via blood transfusion. The sexual cycle can only occur in the tick which makes him the DH (like Plasmodium). The cycle in the white footed mouse is identical to that of humans with the added twist that merozoites can divide by meiosis to form gametes in the mouse, but zygote formation and maturation must occur in the tick. So, we may think of the mouse as the primary IH, and humans as accidental IH.

4. Focus on pathogens: Babesia microti Epidemiology: *found exclusively in areas endemic to the Ixodes deer tick *causes ~200-500 cases annually in the US concentrated around CN, Nantucket Island and other coastal NE locals. *mortality runs ~6.5%, basically all of which are immune suppressed individuals.

5. Focus on pathogens: Babesia microti Pathology / clinical symptoms: *symptoms are not distinctive, therefore history of endemic area and knowledge of possible tick bite are helpful *flu-like or mono-like symptoms: discomfort, fatigue, fever, hepatic dysfunction, decrease RBC count via hemolysis

6. Focus on pathogens: Babesia microti Laboratory diagnosis: *1-3uM trophs in RBCs resembling early ring forms of Plasmodium falciparum *mature trophs characteristically appear as doublets like “rabbit ears” or tetrads – ie. maltese cross formation

7. Focus on pathogens: Babesia microti

8. Focus on pathogens: Pneumocystis carinii Facts / life-cycle: P. carinii is often how referred to as P. pneumonia or PCP. As much as any recognized human pathogen, this is an organism of uncertain affiliation. It has morphological, biochemical and nucleic acid homological characteristics that conflict to resemble both a protozoan and a fungus. We will call it both or neither. Transmission is person to person via cough droplets.

9. Focus on pathogens: Pneumocystis carinii Epidemiology: PCP is an infection of immunosuppressed individuals, particularly AIDS patients. Mortality is high due to severely compromised state of most patients.

10. Focus on pathogens: pathology / clinical symptoms Causes pneumocystosis, among the more common causes of non-bacterial pneumonia is immunocompromised (IC) patients in the US, and is a leading cause of death of AIDS patients. Common symptoms include fever, non-productive cough and hepatosplenomegaly. Histologically, a characteristic alveolar exudate with a foamy or honeycomb matrix property due to the presence of cysts is recoverable. PCP can be rapidly fatal among IC patients, but is treatable in the case of relatively healthy patients.

12. Focus on pathogens: Pneumocystis carinii Laboratory diagnosis: medical history, x-ray, examination of respiratory fluid or biopsy from lungs of affected individuals – stained with Gomori methanomine silver stain or rapid toluidine blue stain. *Trophs: small, pleomorphic to roughly circular with dark central nucleus (may be hard to see). Trophs sometimes 1- 2 microns (sporozoites?), and others 4-5 micron (merozoites?). *Cysts: 6-8 microns, may contain some number of visible trophs intermally. GMS stain stain cyst walls black.

13. Trophs – toluidine blue (top) Cysts – Ag stain & Giemsa (below