SOURCE:
Transfusion Medicine
Volume 12 Issue 2 Page 85 - April 2002
REVIEW ARTICLE

Tick-borne diseases in transfusion medicine

L. Pantanowitz, S. R. Telford III and M. E. Cannon
Summary

Ticks are effective vectors of viral, bacterial, rickettsial and parasitic
diseases. Many of the tick-borne diseases (TBDs) are of significance to
transfusion medicine, either because of the risks they pose to the blood
supply or the necessity for blood products required in their treatment. The
transmission of tick-borne pathogens via blood transfusion is of global
concern. However, among transfusion medicine practitioners, experience with
most of these microorganisms is limited. Transfusion transmission of TBDs
has been documented largely by means of single case reports. A better
understanding of the epidemiology, biology and management of this group of
diseases is necessary in order to assess the risks they pose to the blood
supply and to help guide effective prevention strategies to reduce this
risk. Unique methods are required to focus on donor selection, predonation
questioning, mass screening and inactivation or eradication procedures. The
role of the transfusion medicine service in their treatment also needs to be
better defined. This article reviews the growing body of literature
pertaining to this emerging field of transfusion medicine and offers some
recommendations for transfusionists in dealing with TBDs.

Ticks are haematophagous arthropods with a worldwide distribution. They are
effective vectors of viral, bacterial, rickettsial and parasitic diseases.
As humans encroach more upon their habitats, exposure to many of these
microbes will emerge as significant human pathogens. There are various ways
in which tick-borne diseases (TBDs) may be of significance to transfusion
medicine. Within their human host, many of these microorganisms exhibit a
tropism for either circulating erythrocytes, leucocytes, platelets or their
precursors. The transmission of tick-borne pathogens via blood transfusion
is therefore of global concern (Tables1 and 2). In order for an infectious
agent to be transmissible by blood transfusion, the agent must not only be
present in sufficient quantity in human blood at the time of blood donation,
but it will also need to remain infectious during the processing, storage
and transfusion of the donated blood. However, the risks that TBDs pose to
the blood supply remain largely undefined. A fundamental understanding of
the epidemiology, biology and management of TBDs is necessary to better
assess these risks and help guide effective prevention strategies to reduce
the threat of transfusion transmission. For some TBDs, blood product
administration, including exchange transfusion, and the use of intravenous
immunoglobulin (IVIG) form an integral part of patient management. This
article reviews the growing medical, scientific and zoological literature in
this field that pertains to many of these evolving aspects of transfusion
medicine. Regional approaches currently in place for preventing the
transfusion of TBDs are discussed, and recommendations for transfusionists
dealing with these infections are made.

Tick-borne relapsing fever (TBRF)
Microbiology
Relapsing fever is caused by spirochaetes of the genus Borrelia. Usually
only a single spirochaete is sufficient to initiate relapsing fever
(Barbour, 1999). Borreliae are susceptible to detergents and heat (Barbour,
1999), and have been shown to retain their virulence when frozen at 73°C for
many months (Johnson & Golightly, 2000).

Epidemiology
TBRF occurs throughout much of the world, with the exception of a few areas
in the south-east Pacific, North America (south of the Mason-Dixon line and
east of the Mississippi River), western and central Europe and the Far East.
It occurs in epidemic and endemic forms. Only the endemic form is
transmitted by ticks (of the genus Ornithodoros). The epidemic form is
transmitted by lice. Both transplacental transmission (Scott, 1931) and
spread among intravenous drug users (Lopez et al., 1989) are possible.

Clinical
The incubation period following a tick bite is approximately 1week. Illness
is characterized by recurrent episodes of fever and spirochaetaemia. A rash,
respiratory symptoms, hepatosplenomegaly, elevated liver enzymes, anaemia,
thrombocytopaenia, coagulopathy and CNS involvement may occur. Disease
relapses are owing to the antigenic variation by spirochaetes. By evading
the host immune system in this manner, microorganisms may persist in the
blood for several weeks. Spirochaetes may also protect themselves by hiding
within erythrocyte aggregates (Burman et al., 1998). Borreliae can persist
in locations such as the brain or eye for many years. The fatality rate of
untreated patients may reach 40.

Diagnosis
A definitive diagnosis relies on the demonstration of borreliae in
Giemsa-stained peripheral blood smears. They are most abundant during or
just before a recurrence of fever. Culture and xenodiagnosis (mouse
inoculation) are cumbersome and not readily available, but are highly
sensitive. Serological tests are of limited diagnostic utility owing to the
antigenic variation of strains and high cross-reactivity among species
(Johnson & Golightly, 2000). PCR is now available, but there is little
reported experience with its use (Barbour, 1999).

Treatment
Tetracyclines are the drugs of choice. However, treatment with antibiotics
may be complicated by the Jarisch-Herxheimer reaction.

Transfusion transmission
Numerous cases of TBRF transmitted by blood transfusion have been reported
from Africa (Goldsmid et al., 1974; Hira & Husein, 1979; Aoki & Holland,
1990) and China (Wang & Lee, 1936). The interval between transfusion and the
onset of clinical symptoms appears to be 4-5days (Wang & Lee, 1936). One of
the transfusion recipients was pregnant and miscarried as a result of
acquiring relapsing fever (Wang & Lee, 1936). TBRF can potentially be
transmitted during the transfusion of all blood products, even though
spirochaetes have been shown to settle above or in the same fraction as
platelets after the centrifugation of blood (Chatel et al., 1999).