biology

PART 1 (HEALTHY, IMMUNITY, & DISEASES)

01.    Write an essay on Bilharzias or Schistosomiaisis using the following guidelines.

i.         Life cycle of causative agent

ii.       Transmission of disease                        (NECTA 1995 QN 12)

iii.     Symptoms of disease

iv.     Preventive measures

ANSWER

Bilharziasis is a disease caused by worms called schistosomes, these worms are of three types Schistosoma haematobium which attacks human bladder It is common in East Africa, Egypt and Asia,Schistosoma mansoni attacks large intestine in man and baboons It is common in Middle East and South Americans and Schistosoma japonicum which attacks mainly the small intestine and other parts of alimentary Canal, It is common in china, japans and Philippines.

Transmission of the disease is by the snail, that is the snail disease. Schistosoma eggs are passed with feaces and urine in to water. In water eggs are developed in to worms called miracidia (singular; miracidium), these oval and ciliated worms larvae swim and penetrates in to water snail in which they grow to form cercariae. The larvae cercariae leave a snail and swim in water until they find new person, they penetrate the body through skin  by producing hydrolyzing enzymes which dissolve the skin and enters blood vessel or can penetrates through the  mucus membrane of mouth as one drink dirty contaminated water. Then blood carriesthis cercaria to the pelvic veins where they develop in to adult schistosoma worms.

The symptoms of bilhaziasis can be explain according to the type and a part under which the worms attacks; in urinary Bilharziasis there are pains and sometimes blood is observed during urination due to ulceration of urinary bladder.

In abdominal Bilharziasis there are pains, nausea, loss of appetite and traces of blood in the faeces are observed, other symptoms inclue enlarged spleen, anemia, oedema of feet, swelling of feet due to accumulation of fluid, fever and cough.

Preventive measures, the disease can be controlled through a number of ways these includes,Proper use of latrines, Vector control by draining stagnant water, Avoid bathing in standing water with snail, De-worming that is use of drugs to kill schistosoma in an infected person, Drinking a boiled water, Provision of health education to the community.

02.     Write an essay on either Dysentry or Typhoid using the following outlines

i.         Cause

ii.       Transmission                             (NECTA 1996 QN 11)

iii.     Symptoms.

iv.     Prevention.

v.       Treatment.

ANSWER

AN ESSAY ON DYSENTERY

Dysentery is a disease caused bacterium called Shigella or protozoan known as Entamoeba histolytica, eating contaminated food spreads it or drinking contaminated water.

Transmission of pathogen; these pathogen may be transferred from feaces of an infected person to food by flies or dirty hands, feaces from infected person may also find their way in to water supply and sewage disposal system have been damaged by floods, typhoons and earth quakes.

The symptoms shown by the disease are severe diarrhea with blood stained, abdominal pain, dehydration due to excessive and severe diarrhea and profuse bleeding.

Prevention of disease: the disease can be prevented by proper use of latrines, treatment of sewage system, treatment of domestic water that is water used at home for different purpose, boiling a drinking water, well covering of food to avoid contaminated by flies, washing of fresh foods such as fruits and vegetables before eating and washing hands before and after eating as well as washing with soap after attending toilets.

Treatment, the disease can be treated by rehydration drugs antibiotics.

AN ESSAY ON TYPHOID

Causes of the disease, it is infectious disease caused by bacterium called salmonella typhi; the pathogens attack walls of intestine, spleen, bone marrow and gall bladder. The infected area of small intestine may develop ulcers.

Typhoid is transmitted though drinking contaminated water and eating contaminated food or eating improperly cooed vegetable; the pathogen may also be transferred from feaces of an infected person to food by flies or hands. The vector for typhoid is housefly and it spread through faecal matter of an infected person, may also finds their way in to water used for domestic purpose by unsanitary condition such as poor sewage disposal system, floods, and typhoon. Incubation period is somewhat 1 – 3 months.

Symptoms of the disease shown are as followsContinuous fever for 2 – 3 weeks, Slight abdominal pain or upsets, Vomiting and diarrhea, Sore throat, sometimes bloody stool due to the destruction of the gut and intestinal perforation which accompanied by dysentery. All these symptoms may also be accompanied by irregularity in body temperature.

Prevention of the diseaseare by Proper community sanitation and proper use of latrines, Personal hygiene such as washing hands after visiting toilets with soap and clean water, proper disposal of sewage, Water sources and food should be protected against flies, Water for drinking should be boiled, covering food to avoid contamination, and washing fresh food before eating.

The treatment of the disease is by the use of antibiotics drugs preferably Chlorophenical and also treated by getting vaccination.

03.     Discuss the major sexually transmitted disease under the following guidelines.

a.       Symptoms of the disease.

b.      Possible preventive measures                                     (NECTA 1998 QN 13).

ANSWER.

The major sexually transmitted diseases are Syphilis and Gonorrhea.

Syphilis is a disease appears between 14 to 28 days after contact with infected person, the symptoms of the disease occurs in three stages; the first stage or primary stage last for 3 – 4 weeks after infection, it is characterized by painless sore called chancre, which may appear or around the genitalia, anus or mouth and soon disappear without treatment. The second stage, the stage lasts for 5 – 14 weeks after infection, rashes, fever, weight loss, loss of appetite, body weakness, tender glands and mouth sore, characterize it. The last stage or final stage appear years later when syphilis not treated for long time it starts damaging the internal organs like heart and liver and may results in to blindness, heart disease, and insanity and ectopic pregnancies that is unborn baby dies in the womb or soon after birth and lastly it can lead to death.

The possible preventive measures of the disease are by Abstinence from sex, Being faithful to your partner, Condom use to avoid unprotected sexual intercourse, Avoid contact with skin sores and curing or treatment must be done for all partners which penicillin is effective in the treatment of all stages of syphilis.

Another sexually transmitted disease is gonorrhea, the symptoms for a disease develops in male usually and not in females which includes the following; Burning sensation during urination, Discharge of pus like which are greenish-yellow fluid through urinary system that is tip of the penis in male and vagina in females, It brings about the menstrual change in women, Abdominal pain and swelling. These symptoms appear about 10 days after contact with an infected person.

Preventive measure of the disease includes Abstinence from sex, being faithful to your partner, condom use to avoid unprotected sexual intercourse. Antibiotics can cure gonorrhea and both partners must be treated.

04.     a) What do you understand by the term disease?

b)     Write an essay on various methods by which human infectious disease are transmitted.              (NECTA 1999).

ANSWER

a.       A disease is a condition, which describes the state of health of a body. It is a condition where a part or parts of a body are not functioning normally. Any deviation from the normal functioning of a body means ill health or sickness.

b.      The method under which disease are transmitted are categorized into two ways is direct transmission and indirect transmission into various methods are as follows;

Direct contact; This route for contagious disease that is spread through contact between a health person and infected person for instanceringworms, athlete’s fore tired eyes etc.

Direct bite;this is a direct transmission with a bite from animal contain a disease causing organism e.g. rabies, which is transmitted through dog bite.

Vector borne disease; this is transmission by intermediate agent caused vectorwhich carries a disease for instance female anopheles mosquito carries plasmodium for transmitting malaria, housefly for cholera, tsetse fly for sleeping sickness.

Vehicle borne disease; are disease transmitted to the mouth through a contaminated food, water and other eaten substance e.g. cholera, dysentery and typhoid.

Air bone disease; are disease under which pathogens are spread by wind and dusts for stance tuberculosis, meningitis and influenza.

Formite bone; is a kind of transmission in which person get infection by touching any article which has been in contact with a disease agent e.g. towels, pants, toothbrush etc.

Sexually transmitted disease; are kind of disease transmitted through sexual intercourse with an infected person example AIDS, Gonorrhea and syphilis.

05.     Write an essay on body defense against infections by skin, tears, white bood cells, stomach/ gastric juices and mucus membrane provide a natural body defense against pathogen.                                                                 (NECTA 2001 QN 11)

ANSWER

The skin: skin and epithelial lining provide physical barrier which prevents microbes from entering the body, outer part of the skin is made up of dead layers of cells known as cornified layer, which prevent entry of pathogens in to the body. Sebaceous glands in the dermis secrete Skin sweat and sebum, acts as antiseptic against pathogens.

Tears:are produced by tear glands or lacrimal glands in the eye, can kill foreign organism entering the body through the eyes. they secretes an alkaline fluid which has antiseptic effects on pathogens, when germs enters the eyes they are destroyed by tears.

White blood cells (leukocytes): some white blood cells engulf microbes and destroy them, and othe kind of white blood cells secretes antibodies  which fight against antigens (microbes), and other types of white blood cells produce antitoxins against microbial toxins hence if the toxins of pathogen are neutralized by antitoxins, it brings no harm to the body.

Stomach/ gastric juices: the gastric glands in the stomach produces gastric juice, this juice contain digesting enzyme such as rennin and pepsin and hydrochloric acid, among the function of hydrochloric acid is to kill bacteria that enters the stomach with foodwhich is taken in the body through the mouth.

Mucous membrane:this is the a layer which covers most of the open surface like the inner walls of the digestive system, respiratory system, and the surface of the auditory canal in the ears. The mucous glands in the membrane secretes mucous which traps any pathogens and discharge them out of the body, mucous in the ears secretes ears waxes along the auditory canal to destroy microbes trying to enter to the body through the ears.

06.     Write an essay on cholera using the following guidelines

a.       Causes

b.      Symptoms

c.       Transmission

d.      Effects

e.       Prevention.                                                    (NECTA 2004 QN 12)

ANSWER

Causative agent: Caused by a coma shaped motile bacterium known as Vibrio cholerae.The main source of infection is contaminated water by feaces from infected individual taking contaminated food and water contaminated with feaces from infected person.

The symptoms of the disease areSevere, watery diarrhea passed almost continuously, Whitish stool like rice-water, no abdominal pain, General body weakness, Rapid loss of weight, Wrinkled skin, sunken eyes and cheek due to dehydration, Skin pinch goes back very slowly, Urine is hardly passed or no urine at all, Vomiting after or before diarrhea, this may cause death.

The mode of transmission of cholera is by direct contamination of food or water with feaces  (faecal-oral route) as a result of poor hygienic condition and also by means of vectors e.g. flies moving from human feaces to food. It is very common in crowded areas where poor sanitation and unhygienic condition prevail.

The disease can be preventedby Hygienic waste disposal, Preparing and store food in clean places, Keeping water supply clean and safe, Washing hands thoroughly with soap and water after toilets, Boil a drinking water, Vaccination is also available, Avoid overcrowded areas or burial places during epidermis

The effects of cholera are severe diarrhea, some damage to cells lining the intestine, delaying treatment lead to death.

07.     (a) Out line the ways by which the human body prevents invasion and infection by the disease-causing microorganism.

(b) Discuss the cause, mode of transmission and control of malaria.        (NECTA 2006 QN 13)

ANSWER.

The skin – outer part of the skin is made up of dead layers of cells known as cornified layer, which prevent entry of pathogens in to the body. Skin produce sweat and sebum acts as antiseptic against pathogens.Skin and epithelial lining provide physical barrier which prevents microbes from entering the body, outer part of the skin is made up of dead layers of cells known as cornified layer, which prevent entry of pathogens in to the body. Sebaceous glands in the dermis secrete Skin sweat and sebum, acts as antiseptic against pathogens.

Mucous membrane – the mucous glands in the membrane secretes mucous which traps any pathogens and discharge them out of the body.This is the a layer which covers most of the open surface like the inner walls of the digestive system, respiratory system, and the surface of the auditory canal in the ears. The mucous glands in the membrane secretes mucous which traps any pathogens and discharge them out of the body, mucous in the ears secretes ears waxes along the auditory canal to destroy microbes trying to enter to the body through the ears.

Ciliary membrane – respiratory membrane are equipped with cilia, which traps pathogens and foreign body inhaled with air.

Acids and bacteria in the vagina – the acids provides unfavorable condition for bacteria growth hence preventing new growth of bacteria, the acids also kills foreign organism entering stomach or vagina.

Tears – are produced by tear glands or lacrimal glands in the eye, can kill foreign organism entering the body through the eyes.are produced by tear glands or lacrimal glands in the eye, can kill foreign organism entering the body through the eyes. they secretes an alkaline fluid which has antiseptic effects on pathogens, when germs enters the eyes they are destroyed by tears.

b)     Malaria (causes, transmission and control)

Causative agent;This is caused by protozoon’s parasites known as plasmodium. There are four types of plasmodium, namely, Plasmodium malariae, Plasmodium ovale, Plasmodium vivax, Plasmodium falsiparum

Transmission; Malaria is transmitted by carrying plasmodium from blood of infected person to the new health person through female anopheles mosquito bites, occasionally can occur through blood transfusion.

Control of malaria; Use insecticides to kill adult mosquitoes, Drain mosquitoes breeding grounds, Cut down bushes around homes, Sleeping behind mosquitoes treated nets, Wearing a long sleeved shirts and trousers during nights, Smearing mosquito repellant cream, Introduce fish or tadpoles, frogs and toads, crustacea in water sources. These organism feed oneggs, lava and pupa of mosquitoes.The current treatment in Tanzania is drug of combination of Artemether and Lumefantrine (Alu), second line drug is quinine.

08.     Cholera has been a long-term problem in this country. during heavy rains the problem becomes more serious. Even the neighboring countries have attempted to eradicate the disease but they have not been very successfully.

a.       Explain the possible reasons that have led to the failure.

b.      Explain how this disease can be eradicated successful in terms of its mode of transmission, control and curative methods.

a). Reasons for failure to eradicate the disease are

Poor sanitation: poor sanitation predisposes to more contamination of food and water especially during rainy season when wastes are flashed away by water.

Lack of adequate clean and safe water supplies;people move a long distance searching for water or even pond water that have a risk of contamination especially during a rainy season.

Poor personal hygiene; some people eat fresh foods like fruits, without washing or even eat foods with without washing hands or eating foods sold by mobile vendors where the risk of contamination is very high. Some people don’t wash hands with soap after attending toilet.

Civil unrest; which forces people live in refugee camps on to which the area in most cases are very much congested in creasing a risk to epidemic diseases, example cholera.

Illiteracy; some people have less knowledge concerning the risk of getting cholera, hence have a minima chance of serving themselves from getting a disease.

Poverty; poor incomes compels people to practice which is are non healthy and with a great risk of contaminating cholera, example making and using local brews where its preparation in most cases is not hygienic.

b) Cholera can be eradicated

Education:health education should be provided to people in order to protect them from risky practices.

Sterilization; proper disposal and treatment of feces from cholera victims and all contaminated materials example clothing, bleeding, etc is essential. All material that comes in to contact with cholera patient should be sterilized by washingwith hot water using chlorine bleach if possible. Hands that touch cholera patience or their clothing, bedding should be thoroughly cleaned and disinfect with chlorinated water or other effective antimicrobial agents.

Sewage treatment; antibacterial treatment of general sewage by chlorine, ozone, ultraviolet light, or other effective treatment before it enters a water ways or underground water supplies helps prevent undiagnosed patient from inadvertently spreading the disease.

Water treatment:all water used for drinking cooking or washing should sterilized by either boiling, chlorination, ozone water treatment or antimicrobial filtration in any area where cholera may be present.

Treatment of the patience: in most cases cholera can be treated by the Oral rehydration Therapy (ORT). In situation where commercially produced ORT sachets are too expensive or difficult to obtain, alternative home made solution using various formulas of water, sugar, table salt, baking soda, and fruits offer less expensive method of electrolyte repletion. In severe cholera cases with significant dehydration, the administration of intravenous rehydration solutions may be necessary.

Antibiotics: example tetracycline, shorten the cause of the disease and reduces the severity symptoms, however ORS remains the principle treatment.

09.     (a). Differentiate HIV, AIDS, and STI’s. How do they relate?

(b). Analyse the impacts of HIV/AIDS in the community. What can be done to         controland manage the spread of HIV/AIDS?          (NECTA 2009 QN 12)

ANSWER.

10.     State the cause and explain the transmission (where applicable) and preventive measures of the following problems

a.       Meningitis

b.      Cholera

c.       Malaria                                                               (NECTA 2007 QN 11)

d.      Bilharziasis

ANSWER

a)    Meningitis

b)    Cholera

Cholera is caused by a bacterium known as Vibrio cholerae.

The disease can be transmitted through: Taking contaminated food and water contaminated with feaces from infected person, and through Vectors e.g. flies moving from infected human feaces to food.

Preventive measures of cholera are; Hygienic waste disposal, Preparing and store food in clean places, Keeping water supply clean and safe, Washing hands thoroughly with soap and water after toilets, Boil a drinking water, Vaccination is also availableand alsoAvoid overcrowded areas or burial places during epidermis

c)     Malaria

The disease is caused by protozoon’s parasites known as plasmodium. These parasites are of four types of plasmodium, namely; Plasmodium malariae, Plasmodium ovale, Plasmodium vivax and Plasmodium falsiparum.

Malaria is transmitted by carrying plasmodium from blood of infected person to the new health person through female anopheles mosquito bites, occasionally can occur through blood transfusion.

The Prevention of the are by the following ways; Use insecticides to kill adult mosquitoes, Drain mosquitoes breeding grounds, Cut down bushes around homes, Sleeping behind mosquitoes treated nets, Wearing a long sleeved shirts and trousers during nights, Smearing mosquito repellant cream, Introduce fish or tadpoles, frogs and toads, crustacea in water sources. These organism feed on eggs, lava and pupa of mosquitoes.

d)    Bilharziasis

11.     Explain six factor that affect the immunity of the body in human being.

ANSWER.