Blood is Important for Ticks

Did you know that blood is the meal for many parasites? Unlike most animals that eat a variety of foods to gain energy for survival and reproduction, ticks depend totally on blood. You may even have been bitten by a tick that was trying to obtain food. This blood-feeding behavior, called hematophagy, is essential for their survival, growth, and reproduction. In this article, we will explore the importance of blood for ticks, how they obtain it from their hosts, and the impact that hematophagy can have on the health of both the humans and animals that ticks infest.

What are Ticks?

Ticks are small but fascinating animals that play a unique role in nature. They are ectoparasites, which means they live outside the host’s body, piercing the skin of mammals, birds, and even reptiles to feed on their blood. Ticks have co-evolved with their hosts for over 100 million years. Most tick species can live from 1–2 months to 2–3 years. Interestingly, some tick species can live more than 20 years!

Ticks range in size from a grain of sand to a bean seed. Although many people assume that ticks are closely related to insects (which have six legs), ticks are actually arachnids and therefore more closely related to spiders and scorpions (which are eight legged). They have an oval, globular, flattened body divided into two parts: the head, which contains the mouthparts used for feeding, and the body, which contains up to eight legs in adult ticks. Ticks lack antennae or wings, unlike flies or bees. They are found all over the world and can survive in diverse conditions, from forests and grasslands to urban parks or even backyards [1].

Why do Ticks Need Blood?

Blood is the primary source of nutrition for ticks. Ticks have adapted to consume blood over millions of years of evolution, since the time of the dinosaurs. Unlike other arthropods, which may consume small animals, plant material, or decaying matter, ticks rely solely on blood. Blood provides ticks with essential nutrients, including proteins necessary for tissue growth and development, lipids (fats) used for energy storage and reproduction, and iron, which is vital for many body functions. Therefore, without a blood meal, these animals cannot grow, molt, or reproduce. Young ticks require a blood meal to grow and become mature adults. In the adult stage, males only need small amounts of blood whereas females need large amounts to obtain the nutrients to reproduce and produce thousands of eggs.

How do Ticks Feed?

Once a tick finds a host (Figure 1A), it uses specialized mouthparts to pierce the skin and insert a feeding tube. The mouthparts are made up of several structures, including small teeth that help ticks stay attached to collect and process food. They also have salivary glands that produce saliva to inject into the host, making feeding easier (Figure 1B). The saliva passes to the host through the same channel in which blood is ingested. Some tick species feed for only minutes, while others can feed for several hours or even days.

Feeding and Digestion

When ticks attach to a host animal’s skin, the host usually does not notice their presence, and the blood can flow without interruption. Do you know how they do that? Ticks’ saliva contains substances that numb the area and reduce the pain of the bite, prevent blood from clotting, and suppress the host’s immune response [2]. Insects like mosquitoes, flies, lice, bed bugs, and sandflies feed fast, for seconds to minutes. In contrast, ticks usually feed slowly, sometimes for days, until they are swollen with blood. After feeding, the weight of female ticks can be increased by hundreds of times, and they can then lay thousands of eggs. Unlike mammals, ticks do not have a stomach. Instead, they have a specialized gut called the midgut (Figure 1B) that stores the blood and digests it slowly. This releases nutrients gradually and allows ticks to survive between meals. The proteins and fats from blood are converted into energy, helping them stay alive for days or even months before another blood meal.

What is in Tick Saliva?

Ticks (and other blood-feeding parasites) have a unique saliva that helps them suck blood without getting caught. Tick saliva has substances that prevent blood from clotting, so the blood stays liquid (like a smoothie instead of jelly) during the blood meal, preventing the wound from healing at the tick bite site [3]. Tick saliva also has substances that hide them from the host’s immune system (like Harry Potter’s invisibility cloak), so they are not attacked (Figure 2). Some substances in tick saliva block the itch so the host does not notice the bite right away. They can also spit germs, like the bacteria that cause Lyme disease, into a host while they bite. By weakening the host’s immune defenses, tick saliva can even improve the germs’ survival.

Interestingly, molecules from tick saliva are being studied for several medical uses, including for developing new drugs to prevent blood from clotting and for diseases caused by a malfunctioning immune system.

Ticks feed during their larval, nymphal, and adult stages (please read this Young Minds article) and their saliva composition actively changes during the feeding process. During the first moments, the saliva contains a substance that helps the tick to stick to the skin (the rather unoriginal name of this substance is “cement”). During feeding, the saliva contains anti-clotting substances that keep the blood flowing and anti-immune response substances. The composition of the saliva continually changes. Our research group recently showed that there is an amazing system to adjust saliva components during feeding, in response to host immune reactions [4]. The amount of one substance increases while the other decreases or vice versa, always to escape the host’s defenses—like a very good player in hide and seek. This adaptability is key to tick survival during feeding and allows them to lay thousands of eggs and leave many offspring for future generations.

Why Can Tick-Infested Animals Get Sick?

Do you know why tick-infested animals get diseases? The animals get diseases from the pathogens that are transmitted by ticks as they feed. You might know that when mosquitoes bite, they can transmit viruses to humans, including those that cause malaria or yellow fever. Ticks can also carry and transmit harmful pathogens, including bacteria, viruses, and small parasites, which cause many diseases (e.g., Lyme disease, Rocky Mountain spotted fever, babesiosis, Brazilian spotted fever, East Coast fever, and Texas fever). When a tick feeds on an infected animal or human, it picks up the disease-causing pathogens [5]. The next time it feeds, it can transfer these pathogens to a new host, spreading the disease.

How Do You Properly Remove a Tick?

Properly removing a tick is important to reduce the risk of infection. Use fine-tipped tweezers and avoid using fingers, petroleum jelly, alcohol, matches, or nail polish, as these can irritate the tick and increase the risk of infection. Pinch the tick as close to the skin’s surface as possible, aiming for the head or mouthparts rather than the body (Figure 3). Apply steady, gentle pressure; do not twist, jerk, or squeeze the tick as this can cause the mouthparts to break off or release more germs into the host. If mouthparts remain, try to remove them with tweezers; if left, they usually fall out on their own. After removal, thoroughly wash the area with soap and water or disinfect it with rubbing alcohol. Dispose of the tick by flushing it, sealing it in tape, or preserving it in alcohol (for testing if symptoms develop). It is important to remove the tick within 24–36 h to reduce the risk of disease transmission. If you are unsure of how long a tick has been attached, or if symptoms such as a red rash (with a bullseye pattern), fever, fatigue, or joint pain appear within the next 30 days, consult a medical professional.

Homework and Things to Remember

Blood provides ticks with the nutrients necessary for survival, growth, and reproduction. While feeding on blood is essential for their life cycle, ticks can also spread serious diseases. By understanding how these tiny but potent parasites rely on blood, we can appreciate their role in nature while also taking steps to protect ourselves from infestations and diseases.

Glossary

Hematophagy: ↑ It is when an animal eats blood to survive.

Host: ↑ An organism that provides shelter and nutrition to a parasite.

Ectoparasite: ↑ Parasites that live outside their host’s body.

Molt: ↑ Shedding old skin, shell, or feathers to make room for new, bigger ones.

Immune System: ↑ A shield of cells and molecules working together to chase away bad germs, keeping you from getting sick.

Pathogens: ↑ Disease-causing germs, like bacteria and viruses.

Conflict of Interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

The authors thank Mrs. Stephanie DeBiasio, Maria Antônia Lanzarini Tirloni, and Henry Blankenbaker at Hamilton Middle School for their critical review of the manuscript. This work was partially supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul and Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (Brazil).

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