Question

The Kissing Bug

Josh couldn't believe how much he had learned during his summer volunteer program working in a village clinic in northern Brazil. Even after completing his first year of medical school, Josh was shocked to learn about infectious disease morbidity in this underdeveloped region. He recalled his first appointment of the morning:

Teresa had traveled a long distance to bring her 6-year-old son, Marco, to the clinic. She was very worried because the boy was feverish and irritable but had also suffered from diarrhea and a severely swollen eye for more than a week (see the Figure). Josh was asking Teresa about any recent eye injuries Marco might have sustained as he carefully examined the swelling and struggled to connect the symptoms and make a diagnosis.

Overhearing this conversation, Dr. Thomas stepped into the examining area to assist. He showed Josh several tiny marks near Marco's lips and said, “When you see Romaña's sign, the characteristic swelling around one eye, you'll often find tiny bites around the lips. Marco is in the acute phase of Chagas disease.”

“You mean he's been bitten by the kissing bug,” Josh replied. “I do see the tiny marks now that you've pointed them out. But what is the connection with Romaña's sign?”

Dr. Thomas explained Marco's condition to Teresa and gave her a 30-day supply of nifurtimox with strict instructions to dose Marco four times every day and return to the clinic for a follow-up appointment. “Josh, you need to tell Teresa why it is so important to give Marco the medicine.”

Struggling to translate, Josh told Teresa that Marco's symptoms would eventually disappear on their own, but the microorganism would remain and cause serious damage that would show up in 10 to 20 years when the chronic phase of the infection begins. The only way to prevent this is to take the medicine as directed now. Josh warned Teresa that even though the nifurtimox could cause some unpleasant side effects in Marco, it was very important for her to continue giving the medication according to the directions.

4.  To what long-term damage does Josh refer?

5.  INVESTIGATE: What are the side effects of nifurtimox? Why can they be more problematic in children than adults?

Before they left the clinic, Dr. Thomas also gave Teresa two spray cans of a pyrethroid insecticide with instructions to spray the cracks and crevices in their mud hut once a week.

6.  Why did Dr. Thomas give Teresa insecticide spray?

Please help me understand and answer questions 4,5,6, in detail, thank you

Answer 1

Answers :

4.Long term damage which occurs in chagas disease :

Chronic phase of chagas disease may occur 10- 20 years after initial infection.

Chronic phase include :

• Heart failure : Heart becomes weak and unable to pump enough blood to meet bodies needs.
• Enlargement of esophagus : Also called as megaesophagous.Results in difficulty in swallowing and digestion.
• Enlargement of colon : Also called as megacolon.Results in constipation,severe abdominal pain and distension.

5.Side effects of Nifurtimox :

• Gastric upset(nausea ,vomitings,diarrhea).
• Weight loss ,weakness.
• Sleep disorders.
• Memory loss.
• Convulsions.
• Joint pains.
• Psychosis.
• Polyneuritis and peripheral neuropathy.

The severe side effects like peripheral neuropathy ,psychosis and haemolytic anaemia associated with G6PD deficiency ,are dose dependant ,appear towards end of treatment and resolve after stoppage of treatment.

Mutagenicity : Cytogenetic analysis performed in blood lymphocytes of children given Nifurtimox for treatment of chagas disease resulted in 13 fold increase in chromosomal aberration.

High doses which are given in children for long term may lead to increased incidence of malignant lymphoma.

6.Doctor gave pyrethroid insecticide to spray the cracks and crevices in their mud hut because :

• Chagas disease is caused by parasite Trypanosoma cruzi.
• These parasites are mainly transmitted by contact with faeces or urine of infected blood sucking triatomine bugs.
• These bugs ,vectors that carry the parasites typically live in the wall or roof cracks and crevices.
• Normally they hide during day and become active at night and bite an exposed area of skin such as face hence the name kissing bug.
• These insecticides kill the bugs by effecting their nervous system .