Biology SS 1 Week 6
Topic: Common Diseases
Malaria
Malaria is a mosquito-borne disease caused by a parasite. Malaria is caused by a parasite called Plasmodium, which is transmitted via the bites of infected mosquitoes (Anopheles mosquito). In the human body, the parasites multiply in the liver, and then infect red blood cells
If malaria is diagnosed and treated early on, the duration of the infection can be considerably reduced, which in turn lowers the risk of complications and death.
There are four parasite species that cause malaria in humans:
- Plasmodium falciparum
- Plasmodium vivax
- Plasmodium malariae
- Plasmodium ovale.
Plasmodium falciparum and Plasmodium vivax are the most common. Plasmodium falciparum is the most deadly.
Mode of Transmission
The Anopheles mosquito taking a blood meal
The female Anopheles mosquito transmits the parasite to a human when it takes a blood meal – it bites the human in order to feed on blood.
Only the female Anopheles mosquito can transmit malaria, and it must have been infected through a previous blood meal taken from an infected human.
When the mosquito bites an infected person a minute quantity of the malaria (plasmodium) parasite in the blood is taken.
Approximately one week later that same infected mosquito takes its next blood meal. The plasmodium parasites mix with the mosquito’s saliva and are injected into the host (human being).
Human-to-human transmission of Malaria
As the parasite exists in human red blood cells, malaria can be passed on from one person to the next through organ transplant, shared use of needles/syringes, and blood transfusion. An infected mother may also pass malaria on to her baby during delivery (birth) – this is called ‘congenital malaria’.
People cannot “catch” malaria from others just by being near them. You can sit next to an infected person quite safely, with no risk of infection, even if they cough or sneeze.
Symptoms of Malaria
In regions where Malaria is common, local people usually have some level of immunity, which means that many infected people may have no symptoms at all, or very few.
Severity of Malaria symptoms depends on:
- The type of parasite.
- The individual’s level of immunity.
- Whether the person still has his/her spleen.
Early stage symptoms of Malaria
- A high temperature (fever)
- Chills
- Headache
- Sweats
- Tiredness (fatigue)
- Nausea
- Vomiting
Signs and symptoms tend to be cyclical in severity, during each wave levels of severity may differ. How long symptoms last may also vary, depending on each cycle. Early on during the disease, symptoms may not follow this pattern.
Other common symptoms may include:
- Dry cough
- Back pain
- Muscle ache
- Enlarged spleen
Very rare symptoms may include:
- Impairment of brain function
- Impairment of spinal cord function
- Seizures (fits)
- Loss of consciousness
Patients infected with the P. falciparum parasite are more likely to become seriously ill – their illness can become life-threatening.
Tests and diagnosis
Blood tests can show the presence of the parasite and help tailor treatment by determining:
- Whether you have malaria
- Which type of malaria parasite is causing your symptoms
- If your infection is caused by a parasite resistant to certain drugs
- Whether the disease is affecting any of your vital organs
Some blood tests can take several days to complete, while others can produce results in less than 15 minutes.
Treatments and drugs
The types of drugs and the length of treatment will vary, depending on:
- Which type of malaria parasite you have
- The severity of your symptoms
- Your age
- Whether you’re pregnant
The most common antimalarial drugs include:
- Chloroquine (Aralen)
- Quinine sulfate (Qualaquin)
- Hydroxychloroquine (Plaquenil)
- Mefloquine
- Combination of atovaquone and proguanil (Malarone)
- artemether-lumefantrine (Coartem®)
Preventing Malaria
The two main ways of preventing malaria are:
- Avoiding mosquito bites – this can be achieved in various ways:
- Vector control – this means trying to reduce contacts between people and vectors of disease. A vector is an organism, such as a mosquito, or tick that carries disease-causing microorganisms from one host to another. Controlling mosquito populations can reduce malaria incidence considerably, as well as other mosquito-borne diseases.
- Insecticide-Treated Bed Nets (ITNs) – can significantly reduce malarial infections rates, as well as mortality in endemic areas.
Mother and child under a treated bed net.
Treated nets are considerably more effective than untreated ones. The mosquito can bite the host through untreated nets if there is skin contact with the net.
1. Untreated nets can be penetrated if there are tiny holes. Not only does the insecticide on treated nets kill the mosquito and other insects, it also keeps them away – it is a repellent.
If insecticide-treated bed nets are widely used in an endemic area the mosquito population may drop dramatically, as will their lifespans. This further protects those in the same area who have no treated bed nets.
2. Preventing disease – using anti-malarial medications. These drugs do not prevent the parasite from entering your bloodstream, but they stop it from developing in the blood. This type of prevention is also known as ‘suppression’.
CANCER
Cancer is a class of diseases characterized by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected.
Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumors (except in the case of leukemia where cancer prohibits normal blood function by abnormal cell division in the blood stream). Tumors can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function. Tumors that stay in one spot and demonstrate limited growth are generally considered to be benign.
More dangerous, or malignant, tumors form when two things occur:
- A cancerous cell manages to move throughout the body using the blood or lymph systems, destroying healthy tissue in a process called invasion
- That cell manages to divide and grow, making new blood vessels to feed itself in a process called angiogenesis.
When a tumor successfully spreads to other parts of the body and grows, invading and destroying other healthy tissues, it is said to have metastasized. This process itself is called metastasis, and the result is a serious condition that is very difficult to treat.
Types of Cancer
This list of common cancer types includes cancers that are diagnosed with the greatest frequency
Bladder Cancer
Breast Cancer
Endometrial Cancer
Kidney Cancer
Leukemia (Blood cancer)
Lung Cancer
Melanoma (skin cancer)
Pancreatic Cancer
Prostate Cancer
Thyroid Cancer
Risk factors
Doctors often cannot explain why one person develops cancer and another does not. But research shows that certain risk factors increase the chance that a person will develop cancer. These are the most common risk factors for cancer:
- Growing older
- Tobacco
- Sunlight
- Ionizing radiation
- Certain chemicals and other substances
- Some viruses and bacteria
- Certain hormones
- Family history of cancer
- Alcohol
- Poor diet, lack of physical activity, or being overweight
Many of these risk factors can be avoided. Others, such as family history, cannot be avoided. People can help protect themselves by staying away from known risk factors whenever possible.
Symptoms
Symptoms and signs of cancer depend on the type of cancer, where it is located, and/or where the cancer cells have spread. For example, breast cancer may present as a lump in the breast or as nipple discharge. A few patients show no signs or symptoms until the cancer is far advanced.
The American Cancer Society describes seven warning signs that a cancer may be present, and which should prompt a person to seek medical attention. The word CAUTION can help you remember these.
- Change in bowel or bladder habits
- A sore throat that does not heal
- Unusual bleeding or discharge
- Thickening or lump in the breast, testicles or elsewhere
- Indigestion or difficulty swallowing
- Obvious change in the size, colour, shape
- Nagging cough or hoarseness
Other signs or symptoms may also alert you or your doctor to the possibility of your having some form of cancer. These include:
- Unexplained loss of weight or loss of appetite
- A new type of pain in the bones or other parts of the body which may be steadily worsening, or come and go, but is unlike previous pains you may have had before
- Persistent fatigue, nausea or vomiting
- Unexplained low-grade fevers with may be either persistent or come and go
- Recurring infections which will not clear with usual treatment
Treatment of Cancer
Cancer treatment depends on the type of cancer, the stage of the cancer (how much it has spread), age, health status, and additional personal characteristics. There is no single treatment for cancer, and patients often receive a combination of therapies and palliative care. Treatments usually fall into one of the following categories: surgery, radiation, chemotherapy, immunotherapy, hormone therapy, or gene therapy.
- Radiation: Radiation treatment, also known as radiotherapy, destroys cancer by focusing high-energy rays on the cancer cells. This causes damage to the molecules that make up the cancer cells and leads them to commit suicide.
- Chemotherapy: Chemotherapy utilizes chemicals that interfere with the cell division process – damaging proteins or DNA – so that cancer cells will commit suicide. These treatments target any rapidly dividing cells (not necessarily just cancer cells), but normal cells usually can recover from any chemical-induced damage while cancer cells cannot.
- Immunotherapy: Immunotherapy aims to get the body’s immune system to fight the tumor. Local immunotherapy injects a treatment into an affected area, for example, to cause inflammation that causes a tumor to shrink.
- Hormone therapy: Several cancers have been linked to some types of hormones, most notably breast and prostate cancer. Hormone therapy is designed to alter hormone production in the body so that cancer cells stop growing or are killed completely.
- Gene therapy: The goal of gene therapy is to replace damaged genes with ones that work to address a root cause of cancer: damage to DNA.
- Surgery: Surgery is the oldest known treatment for cancer. If a cancer has not metastasized, it is possible to completely cure a patient by surgically removing the cancer from the body. This is often seen in the removal of the prostate or a breast or testicle. After the disease has spread, however, it is nearly impossible to remove all of the cancer cells.
