1. Human Babesiosis – An Update Patricia J
Human Babesiosis – An Update Patricia J. Holman Department of Veterinary Pathobiology College of Veterinary Medicine and Biomedical Sciences Texas A&M University College Station, TX

2. Babesiosis Emerging tick-borne disease
Zoonosis caused by intraerythrocytic protozoan parasites
Infections may range from asymptomatic to severe, or even fatal
Most cases occur in the U.S.;
worldwide where ticks occur

3. Phylum – Apicomplexa Babesia, Plasmodium, Toxoplasma, Cryptosporidium
Unique organelles comprise apical complex
Electron micrograph
courtesy of
Dr. R.E. Droleskey
USDA
College Station, TX

4. Babesia - Two-host life cycle
Sexual reproduction in the vector tick Asexual reproduction in
mammalian red blood cells

6. Babesia divergens Tick transovarial transmission

7. Babesiosis Symptoms 1-6 wks after tick feeds Variable
Asymptomatic infection
Mild to moderate illness
Severe disease – usually immunosuppressed
Medication
Splenectomy
HIV co-infection
Malignancy

8. Babesiosis Symptoms Clinical Presentation May last a week or months
Fatigue
Intermittent fever
Chills, sweats, headache, arthralgia, anorexia, cough, nausea Asymptomatic infection
Clinical Presentation
Fever, pallor
Splenomegaly
Hepatomegaly
May last a week or months
Prolonged recovery; persistent parasitemia

9. Babesiosis – Severe form
Most common complications
Respiratory failure
Congestive heart failure
DIC
Liver and kidney failure
Splenic rupture
Immunocompromised – 21% mortality

10. Diagnosis CBC Blood chemistry
Hemolytic anemia with elevated reticulocytes
Thrombocytopenia
Normal to slightly decreased leukocyte count
Blood chemistry
Elevated serum liver enzymes (~ ½ of patients)
Proteinuria, elevated blood urea nitrogen and serum creatinine

11. Microscopic identification
Diagnosis
Microscopic identification
Giemsa stained thick or thin blood films
Babesia ring forms can be mistaken for malaria
Serology - IFA
B. microti
B. duncani does not cross-react
B. divergens
Sera from B. divergens or B. ventorum patients cross react

12. Polymerase chain reaction
Diagnosis
Polymerase chain reaction
Highly sensitive and specific
Useful for extremely low parasitemias
Confirm infection
Determine species
FISH
Detects Babesia DNA in patient blood film
Specific probe binds to DNA
Highly specific; not as sensitive as PCR
IGeneX

13. Diagnosis Subinoculation into laboratory animals
2-4 weeks for parasites to appear in circulation
Hamster – Babesia microti
No known laboratory host for all of the human Babesia spp.

14. Treatment Atovoquone/azithromycin 7-10 days
B. microti infections
15% adverse reactions
Diarrhea and rash
Clindamycin/quinine 7-10 days
Recommended for severe babesiosis
72% adverse reactions
Diarrhea; tinnitus and hearing loss
Exchange transfusion - severe illness

15. Prevention Avoid areas with ticks, mice and deer Anti-tick strategies
Especially May-October
Especially immune compromised people
Anti-tick strategies
Long sleeves, long pants tuck cuffs into socks
Pyrethrins on clothing
DEET on exposed skin
Check for and remove ticks promptly after possible exposure

16. Prevention II Property Keep grass short Remove leaf litter
Discourage mice
Seal potential den holes
Pyrethrin treated cotton
Discourage deer
“Deer proof” plants
Fencing

17. Prevention III Transfusion risk No FDA approved test for donated blood
Agencies prohibit donations by people
who live in or visit endemic areas
Research ongoing for ways to inactivate
organisms in blood

18. Zoonotic Babesia spp. Europe Asia, Africa, and South America
Babesia divergens - France, Ireland, Great Britain (cattle production)
Babesia venatorum – Austria, Italy, Germany
Babesia microti
Asia, Africa, and South America
Babesia microti-like
B. divergens-like
Ovine Babesia-like

19. Babesia divergens Most cases occur in France & British Isles Hosts
30 reported human cases
Associated with cattle
84% asplenic patients; 42% fatality rate
Infection is considered a medical emergency
Hosts
Cattle, small mammals
Ixodes ricinus

20. Babesia venatorum Three documented cases
All asplenic and > 50 years
Mild to severe, but not fatal
Parasites – typical paired pyriform
Hosts
Roe deer
Ixodes ricinus

21. Zoonotic Babesia spp. United States Babesia microti - Northeast
and upper midwest
Babesia duncani – Washington state (WA1-3)
California CA1-6 (similar to B. duncani ?)
Babesia divergens-like – MO-1 and KY
(Nantucket Island)
Babesia divergens-like –
Washington state

22. Babesia microti Most cases occur in the U.S.
> 300 known cases – not a reportable disease
Variable severity of disease
Most symptomatic cases mild and self-limiting
Immune suppressed or >50 yrs at higher risk of severe disease
5% mortality rate
Tick transmission May-October
Transfusion or blood product associated cases
Neonatal cases

23. Babesia microti U.S. endemic regions
Ixodes scapularis
White footed mouse
White-tailed deer maintain the vector tick
B. microti cannot infect deer
Parasites in tetrads in “paired” form

24. Babesia microti Not considered a major human pathogen in Europe
High prevalence in rodents
Ixodes trianguliceps vector tick – nest dwelling
Ixodes ricinus

25. Babesia duncani Washington and California Five cases
Spleen intact individuals
Subclinical to severe illness
2 were acquired via transfusion
Seroprevalence 4 to 17%
Tick vector and reservoir host unknown
Parasites in tetrads in “paired” form

26. Babesia divergens-like
One case in Washington state
Asplenic, > 50 years
Similar molecularly to Babesia divergens
Tick and reservoir host not known

27. Babesia divergens-like
Two cases - MO-1 and KY
Both asplenic, > 50 years
Both severe disease, 1 death
Parasite endemic on Nantucket Island
Eastern cottontail rabbits
Ixodes dentatus
Not infective to cattle
No human cases on Nantucket Island

28. Babesia divergens-like cases of Human Babesiosis
KY isolate
Critically ill man admitted to emergency room in Kentucky
Fever
Chills
Bloody urine
Immediately started on doxycycline – Ehrlichiosis?

29. Babesia divergens-like KY
Blood smear - Numerous babesia organisms
History
Splenectomy 9 years previously
Tick exposure
Recreational hunter
WTD and cottontail rabbits

30. Diagnosis and Treatment
Negative for Ehrlichia and Babesia microti
*** Babesia divergens *** (Beattie et al. 2002)
Pathology - Asplenic
Morphology
18S rRNA gene sequence
Hospitalized for 12 days
TX: Clindamycin, quinine, and doxycycline

31. B. divergens-like MO-1 MO-1
Fever, chills, headache, sore throat, and joint pain
No improvement with erythromycin
Fatal infection (Herwaldt et al, 1996)
MO-1 18S rRNA gene identical to KY

32. B. divergens-like NR Nantucket (rabbit isolate)
KY/MO-1 18S rRNA gene identical to NR
(Goethert & Telford 2003)
16% of rabbits positive by PCR
Ixodes dentatus ticks, larval to nymphal stage 4% +

34. Babesia divergens Discrepancies
Tick vector ?
Neither patient had traveled outside of the US
No known infection in U.S. cattle despite high cattle population in Kentucky and dairies on Nantucket Island

35. rRNA ITS1 & ITS2 Percent Identities
SSUrRNA
ITS1
5.8S
ITS2
LSUrRNA
rRNA ITS1 & ITS2 Percent Identities KY NR
Bdiv
100 94 90

36. Infection Studies Source of parasites needed No blood from the case
Rabbits
Limited by extremely low circulating parasitemias
In vitro culture
Produce quantities for additional characterization
Collaboration with Goethert and Telford, Tufts University

37. Host erythrocyte specificity in vitro
Parasite
Host RBC
Serum supplement
Nantucket
Rabbit
(NR774)
B. divergens
Human
Bovine
Cottontail rabbit
Growth
Yes No

38. Results - Morphometric
Parasite
Host RBC
Size Stddev NR
Human
Cottontail rabbit
Bovine
4.3 µm ± 0.48
4.2 µm ± 0.56
N/A
Bdiv
3.1 µm* ± 0.53
2.2 µm ± 0.36 KY
Human (blood)
4.1 µm ± 0.58

39. Cattle Infection Study

40. Conclusions KY and NR are conspecific B. divergens distinct
Identical 18S rRNA gene sequence
Identical ITS1 / ITS2 sequences
Size - large babesia
Morphology
B. divergens distinct
ITS1 and ITS2 sequences vary from KY/NR
Size - small babesia in natural host
Infective for cattle
Culture – Bovine RBC, not cottontail rabbit

41. Babesia divergens is not endemic in the U.S.

42. Acknowledgements
Dr. Andy Allen, Washington State University, Pullman, WA
Dr. Jim Beattie, Bowling Green Associated Pathologists, KY
Dr. Bob Droleskey, USDA, College Station, TX
Dr. Heidi Goethert, Tufts University, MA
Dr. Sam Telford, Tufts University, MA
Dr. Will Goff, USDA, Pullman, WA
Dr. Don Knowles, USDA, Pullman, WA
Angela Spencer & Lorien Schoelkopf
Funding: NIH RO3, USDA/ARS, Texas Agricultural Experiment Station