Overview of Tick
Ticks are invertebrates in nature, normally 3 to 5 mm long and they belong to Kingdom Animalia.
Systematic Position
Phylum: Arthropoda
Class: Arachnida
Sub-Class: Acari
Order: Ixodida
There are nearly 18 tick genera and about 850 different species. Ticks are external parasites and their source of feed is the blood of mammals, reptiles, amphibians, and birds. Body of Adult tick is ovoid or pear-shaped, having 8 legs.
They are distributed among two major families, Ixodidae namely hard ticks and Argasidae namely soft ticks.
Hard ticks have their mouthparts at the frontal position, while soft ticks have their mouthparts underlying their body.
The life cycle of a tick is completed after four stages namely egg, larva, nymph, and adult, it requires more than a year to complete a full life cycle.
Stages in the Life Cycle of Ticks
The First Stage (egg)
The adult female tick first fulfills a proper blood meal then the process of mating occurs between an adult male and adult female tick. The female tick then leaves the host and lays eggs in a suitable spot outside the host.
The Second Stage (larva)
The eggs are hatched marking the beginning of a six-legged larval stage within a time span of 2 to 8 weeks. After hatching, the larva then remains on the grass waiting for a suitable host to attach. The odor of the host enables the tick to determine the host to get attached with. After attaching to host the larva feeds upon it and undergoes several stages of molting to transform into a nymph.
Third Stage (nymph)
The larva after feeding on the host for several days acquires a good blood meal and then detaches itself from the host to molt into an eight-legged nymph. The larva molts for two weeks until it develops into an eight-legged nymph and again searches for a suitable host to get attached with for initiation of the next stage.
Fourth Stage (adult)
At this stage, the tick or larva is sexually matured and sufficient enough to reproduce. When it comes to hard ticks, the male and female ticks first acquire a sufficient blood meal and then initiates the process of mating.
Usually, a female tick takes a longer time of feeding compared to the male tick. After the mating process male tick dies, while the female tick dies after laying eggs.
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The life cycle of Tick
Tick-Borne Diseases
As ticks feed on blood meals they transmit a number of infections to the host caused by pathogens like bacteria, viruses, and protozoa.
Some ticks carry pathogens that can cause human diseases namely.
Anaplasmosis
Transmitted to humans mainly by the bite of black-legged ticks. It is mainly a bacterial type of disease that attacks the white blood cells in the body. Symptoms include fever, chills, muscle pain, headache, fatigue, and stomach pain.
Babesiosis
It is a protozoan type disease caused by Babesia microti parasite mainly transmitted by black-legged ticks. Symptoms include low blood pressure, anemia, and flu-like symptoms.
Colorado tick fever
It is a viral infectious disease caused by the colorado tick fever virus transmitted to humans by Rocky Mountain wood ticks.
Ehrlichiosis
Transmitted to humans by lone star ticks. Symptoms mainly include fever, headache, nausea, stomach pain, and diarrhea.
Lyme Disease
The most common tick-borne disease is Lyme disease, It is a bacterial type disease mainly caused by deer ticks.
Symptoms include Fever, migraine, cranial nerves palsy, carditis, fatigue, influenza-like illness, and rash, which later gets bigger and appears as a circular red ring.
Tick-Borne Relapsing Fever (TBRF)
It is also a bacterial type of disease. Transmitted to humans through the bite of infected soft ticks mainly of Ornithodoros species. Symptoms include recurring high fever, rigors, headaches, muscle, and joint pain, flu-like symptoms.
Powassan Disease
It is transmitted to humans by groundhog ticks and black-legged ticks. A type of viral infectious disease. Symptoms include fever, headache, vomiting, loss of coordination, and seizures.
Rocky Mountain Spotted Fever (RMSF)
Transmitted by the Rocky Mountain wood ticks, American dog ticks, and brown dog ticks. Symptoms include fever, headache, myalgia, altered mental status, and rash.
Tick-Borne Encephalitis (TBE)
It is caused by the TBE virus and is transmitted to humans through infected species of ticks called Ixodes.
Tularemia
Transmitted to humans by dog ticks, wood ticks, and the lone star ticks. Symptoms include fever, skin ulcer, swelling in glands (lymph nodes).
Did You Know?
Nutrition of ticks fully depends upon blood meals, they feed upon the blood of mammals, reptiles, amphibians, and birds.
Ticks cannot survive on a single host for their entire lifespan therefore they change their host at every different stage of their life cycle as they totally depend upon the host for feeding and growing.
Ticks after every stage search a potential host to get attached with, lying on the grasslands they wait for the suitable host to arrive, and once they identify the odor of butyric acid of any mammals they get attached to it.
An adult female tick can lay several thousand eggs from 2000 to 18000 approximately during its entire lifespan.
Ticks prefer warm and moist areas to live. In humans, they are mostly found in armpits, groin, or scalp.
FAQs on Tick Life Cycle
1. What are the four main stages of the tick life cycle?
The tick life cycle progresses through four distinct stages: egg, larva, nymph, and adult. It begins when a female tick lays eggs, which hatch into six-legged larvae. After feeding on a host, the larva moults into an eight-legged nymph. The nymph requires another blood meal to moult and develop into a mature eight-legged adult, which can then reproduce, completing the cycle.
2. How long does a complete tick life cycle usually take?
The duration of a tick's life cycle can vary significantly based on the species, number of hosts, and environmental factors like temperature and humidity. For a common three-host tick, the entire cycle can take up to three years to complete. However, one-host ticks may complete their entire life cycle in less than a year, as they do not need to find a new host for each stage.
3. What is the significance of a blood meal for a tick's development?
A blood meal is crucial for a tick's survival and progression through its life stages. It provides the essential nutrients required for growth and energy. Ticks must feed on blood to transition from the larval stage to the nymphal stage, and again from the nymphal stage to the adult stage. For adult females, a final blood meal is necessary to acquire enough protein and lipids to produce and lay thousands of eggs.
4. How does a one-host tick's life cycle differ from a three-host tick's life cycle?
The primary difference lies in the number of individual animals they feed on.
- A one-host tick remains on the same animal for its entire life, from larva to nymph to adult, only leaving after its final blood meal to lay eggs.
- A three-host tick is more complex; it attaches to a different host for each of its active stages (larva, nymph, and adult). It feeds, drops off, moults in the environment, and then seeks a new host for the next stage. This increases the tick's role as a disease vector.
5. What is "questing" and how does it help a tick find a host?
Questing is the primary host-finding behaviour of ticks. A tick climbs to the top of a blade of grass or a leaf and extends its front legs, waiting for a potential host to pass by. It detects hosts through body heat, carbon dioxide, and vibrations. When a host brushes past, the tick latches on. This behaviour is critical for its survival, as it must successfully find a host at each active stage to get a blood meal and continue its life cycle.
6. What are the key characteristics of a tick larva compared to a nymph?
The main differences between a tick larva and a nymph are their size and number of legs. A larva is the first stage to hatch from the egg. It is very small, often the size of a pinhead, and has only six legs. After its first blood meal, it moults and becomes a nymph, which is larger and has eight legs, just like an adult tick. The nymph is sexually immature.
7. Why do ticks require specific environmental conditions like high humidity to thrive?
Ticks are highly susceptible to dehydration. They require an environment with high humidity (typically above 80%) to absorb moisture from the air and stay hydrated, especially during the long periods when they are off a host and waiting to moult or find a new one. Low humidity can cause them to dry out and die, while low temperatures can halt their development, preventing eggs from hatching or larvae from moulting. This is why they are most active in warm, damp, and shaded areas.
8. Where do female ticks typically lay their eggs, and why is the location important?
After her final blood meal, an adult female tick drops off the host and seeks a protected location to lay her eggs, a process called oviposition. She typically chooses sheltered spots on the ground, such as in leaf litter, under rocks, or in dense vegetation. The location is vital because it must provide sufficient moisture and protection from predators and extreme temperatures to ensure the eggs can survive and hatch into larvae.
9. What role does moulting play in the transition between tick life stages?
Moulting, or ecdysis, is the process of shedding an exoskeleton and is essential for a tick's growth and development. A tick cannot grow larger within its rigid outer shell. After obtaining a sufficient blood meal, the tick detaches from its host and finds a safe place to digest the blood and begin the moulting process. This allows it to transform from a larva to a nymph and from a nymph to an adult, with each new stage being larger and more developed.
10. Why do male ticks often have a shorter lifespan than females?
The difference in lifespan is linked to their reproductive roles. The primary function of an adult male tick is to find a female and mate, which often occurs on a host. Many male ticks die shortly after mating. In contrast, an adult female tick must consume a large blood meal to mature her eggs. She lives longer to complete this feeding process and then find a suitable location to lay several thousand eggs, ensuring the continuation of the species before she dies.
