Tick-borne diseases in transfusion medicine

[Guest guest]

"......... Spirochaetes may also protect themselves by hiding

within erythrocyte aggregates ..."

 

"......A rash,

respiratory symptoms, hepatosplenomegaly, elevated liver enzymes, anaemia,

thrombocytopaenia, coagulopathy and CNS involvement may occur. ......."

 

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).