TICK-BORNE PARASITIC INFECTIONS

BY

UWAMOSE,Martin Nelson Osaigbokan

AUGUST , 2014

INTRODUCTION

Tick-borne parasitic infections occurs throughout the world, with approximately 5,000 to 12,000 reported cases per year in Europe.

The vector, tick which is a small arachnid belongs to the order Parasitiforms.

It is blood sucking ectoparasite that can not survive and move from one stage to another without a blood meal. It is thus described an obligate parasite and are therefore an excellent vector for disease transmission.

There are two well known parasitic infections that are tick-borne, they are: Babesiosis, caused by the protozoan parasites of the genus Babesia and Theileriosis, caused by Theileria species.

These parasitic infections are known to infect animals such as cattle, causing milk reduction and growth decrease and also humans.

EPIDEMIOLOGY

Risks of tick-borne infection is not uniform throughout the world. It occurs in tropical and subtropical areas of the world. They are also prevalent in many temperate areas such as northern Europe and France. The highest risk is in Europe where there are about 5,000 to 12,000 cases each year (L’ Hostis and Seegers 2002).

Figure 1: Geographical distribution of ticksSource: Google images

Geographical distribution of Ticks

Hyalomma Ticks vector presence

Serological evidence and vector presence

5000 – 12000 cases reported per year

12000 and more cases reported per year

BIOLOGY OF TICKS Ticks are small arachnids in the order Parasitiforms. Approximately 800 species have been described

worldwide with only two well established family; Ixodidae (the hard ticks) and Argasidae (the Soft ticks).

They are obligate ectoparasites that feeds on the blood of mammals, birds and reptiles and transmits wide variety of pathogens.

They extract the blood of their host by cutting a hole into the host epidermis and inserting the hypostome. They keep the host blood from clothing by excreting an anticoagulant.

Blood is a major requirement for ticks survival and moving from one stage of their life to the next.

LIFE CYCLEThe two well established of ticks undergo three primary stages of development: Larval, Nymph and adults.

For Ixodid ticks, it requires three hosts and their life cycle takes at least one year to complete.

The adult female ticks can lay up to 3,000 eggs on the ground.

The larvae emerge, feeds on small mammals and birds after which they detach from their host and molt to nymph on the ground

The nymph feed on larger hosts and molt to adult

The adult attach to larger hosts, feeds very little and occupy the host primarily for mating.

Figure 2: Larva (A), nymph (B), adult male (C), adult female (D) and engorged adult female with eggs (E) of I. scapularisSource: CDC images

Figure 3: Typical Ixodid tickSource: Google images

Figure 5: Typical life cycle of tick

TICK-BORNE PARASITIC DISEASES

There are only two known tick-borne parasitic diseases of great economic importance in the world.

Babesiosis

Theileriosis

BABESIOSIS

BabesiosisCAUSES:

Babesiosis is caused by parasitic protozoa of the genus Babesia.

It is transmitted by deer tick, Ixodes scapularis

Many different species of Babesia parasites have been found in animals with only a few found in people.

SYMPTOMS:

They ranges from fever, chills, headache, muscle pain, nausea, cough, sore throat, to rash in 30% to 40% of adults.

TREATMENT

Treatment is with anti-babesial drugs, the combination of atovaquone and azithromycin, anti-babesiosis vaccines.

Tick control through insect repellent.

THEILERIOSIS

TheileriasisCAUSES:

Theileriasis is caused by an obligate intracellular protozoan parasites of the genus Theileria.

It is transmitted by ticks of the genus Hyalomma.

The two most pathogenic and economically important Theileria species are T. parva and T. annulata.

T. parva occurs in Eastern and Southern Africa while T. annulata occurs in North Africa, southern Europe and Asia.

SYMPTOMS:

Theileriosis should be suspected in tick–infested animals with a fever and enlarged lymph nodes. Others includes lacrimation, nasal discharge, and diarrhea.

TREATMENT

Treatment is with chemotherapeutic agents such as buparvaquone.

Tick control through insect repellent can also be used

GENERAL DIAGNOSIS

Tick-borne parasitic infections can be diagnosed by the identification of the causative agent of the parasites in Giemsa-stained blood smears, Polymerase chain reaction (PCR) test, Indirect fluorescent antibody (IFA) test, serology and lymph node needle biopsy smears especially for Theileria parasites (WHO 2008).

PREVENTION OF TICK-BORNE PARASITIC INFECTIONS

Prevention strategies for tick-borne diseases can be divided into 3 general categories: Environmental, Personal, and Prophylactic (after a tick bite has occurred) Environmental strategies involves the control of the

population of deer and other vector and tick control measures.

Personal strategies involves avoiding grassy areas with shrubs that attract ticks, wearing long trousers and socks, applying permethrin (an insect repellent) to clothing.

Prophylactic measures include the use of vaccines.

CONCLUSION

Scientist should put in more efforts in the study of the epidemiology and distribution of tick-borne parasitic infections as there is a growing population of ticks because people build homes where tick and their host inhabit. Awareness should therefore be made to people living such areas about risk of tick-borne parasitic infections. Parasite causing agent of the infections should be studied for better ways of treatment and control strategies.