Siobal, John Cedrick S.
BSBIO 4-1MB
Long Exam 5
1. Select a particular pathogen (bacteria, virus, fungi, or protozoan) that may be food-borne).
Discuss its biology, epidemiology, signs, and symptoms, diagnosis, prevention and control
measures, and how does it cause disease to the exposed individual.
Hepatitis A Virus (HAV) is highly contagious, and is the leading cause of hepatitis, out of
all its other types. Recurring or epidemic outbreaks of HAV arise mostly in developing countries
and has dropped prevalence to regions with access amended water treatment and employs
good hygiene. HAV usually cause short-term, and self-limiting illnesses that are resolved within
4-7 weeks without permanent damage to the individual (Gholizadeh et al., 2023).
Figure 1. Hepatitis A Virus under Electron Microscope (Gilroy, 2019)
a) Biology – HAV is small and nonenveloped virus belonging to Picornaviridae family under
the genus Hepatovirus. Its diameter ranges from 27-32nm. It has one serotype with six
genotypes, but only genotypes I-III can infect humans. (Gholizadeh et al., 2023).
b) Epidemiology – Millions of people contract HAV through contaminated food and water.
The infection rate is closely linked to access to safe drinking water and socioeconomic
factors. High-income regions have low HAV endemicity (< 50% of population), while lowincome regions have high endemicity (> 90% of population). Middle-income regions
exhibit both intermediate and low levels of endemicity. Globally, there are only 1.5
million reported clinical cases of HAV each year, but the actual infection rate is much
higher. In highly endemic countries, nearly all children become infected at a young age,
usually without symptoms, but develop lifelong immunity. Paradoxically, in low endemic
countries, most children and adults remain vulnerable to symptomatic infection, leading
to a higher disease burden (Jefferies et al., 2018).
c) Signs and symptoms - Individuals infected with HAV may experience a range of signs and
symptoms. The incubation period is typically 14-28 days. Symptoms of hepatitis A
include fever, malaise, lack of appetite, diarrhea, nausea, stomach pain, dark-colored
urine, and jaundice (yellowing of the skin and whites of the eyes). In children, primary
HAV infection is often asymptomatic, while in adults, it can lead to acute hepatitis A
(AHA) and severe liver damage. Infected children under the age of six usually show no
symptoms, while older children and adults may experience more severe symptoms such
as jaundice, fever, and diarrhea. Some individuals may also develop nontypical clinical
characteristics, such as recurrent hepatitis, prolonged cholestasis, or extrahepatic
symptoms. In rare cases, HAV can lead to severe clinical hepatitis and death, but chronic
hepatitis or persistent infection is uncommon. While complications such as nephrotic
syndrome, glomerulonephritis, vasculitis, pancreatitis, Guillain–Barré syndrome,
thrombocytopenia, or aplastic anemia are rare, they can have long-term consequences.
Fulminant liver failure, characterized by encephalopathy, jaundice, and an increased
international normalized ratio (INR), occurs in about 1 percent of HAV infections and is
more likely in individuals with underlying liver disease or older age. Most cases of HAV
infection resolve on their own with supportive treatment, and infected individuals
develop long-term immunity. However, a small percentage of cases may experience
relapse, characterized by recurring infections with milder symptoms, elevated liver
enzymes, and the possibility of extrahepatic symptoms (Poortahmasebi et al., 2023).
d) Diagnosis – Poortahmasebi et al. in 2023 stated in their research that diagnosis of HAV
can be done by the following:
• Antibody detection: HAV-specific IgM antibodies are detected in the early stage of
the disease and can last for six months after infection. IgG antibodies can last for
many years. Enzyme-linked immunosorbent assay (ELISA) and rapid tests based on
immunochromatographic technologies are used to detect antibodies.
• Liver enzyme levels: Measurement of liver enzyme levels such as ALT, alkaline
phosphatase (ALP), gamma-glutamyl transpeptidase (GGTP), and serum bilirubin.
• Antigen detection: PCR and nucleic acid hybridization assays are used to identify
HAV antigens. Molecular assays, such as real-time PCR, that directly detect viral
nucleic acids can improve diagnosis.
• HAV identification in food: Molecular tests, including conventional PCR and
quantitative RT-PCR (RT-qPCR) using fit-for-purpose primers and fluorescent probes,
are used to detect HAV in food. RT-qPCR is considered the gold standard for HAV
detection in food.
• Other diagnostic methods: Cell culture, biosensors, and molecular fluorescence
sensors are mentioned as various approaches used to determine viruses, including
HAV.
e) Prevention and control measures – There are several ways to control and prevent HAV,
5 of which are discussed by Poortahmasebi et al (2023).
• Vaccination: Hepatitis A vaccination is recommended for various populations,
including children above the age of one, individuals at risk (such as travelers to highrisk areas, people with homosexual tendencies, those consuming illegal substances,
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and individuals with chronic liver disease), and adults who want to avoid hepatitis A
infection. Vaccines such as Havrix, Vaqta, and Twinrix (which provides dual
protection against HAV and HBV) are available.
Heat treatment and sanitation: Heating foods to at least 185 Fahrenheit for at least
1 minute, chlorinating contaminated water, and washing contaminated surfaces
with a bleach-water solution can help eliminate HAV.
Nutrition: Certain nutritional factors, such as Japanese miso extracts, have been
shown to inhibit HAV replication by boosting the expression of GRP78, a protein that
inhibits HAV growth. This suggests that incorporating certain dietary supplements
may be helpful in treating severe hepatitis A.
Antiviral medication: Although hepatitis A vaccines are effective, antiviral
medications are being explored as potential treatments. Direct-acting antivirals
(DAAs) and host-targeting agents (HTAs) are being investigated as potential options,
but currently, there are no known cures for hepatitis A. Supportive care and avoiding
unnecessary medication are important aspects of treatment.
Safe sexual practices: While common sexually transmitted disease prevention
techniques may not be sufficient to prevent HAV transmission, they are important
for education and awareness, particularly for individuals engaged in high-risk sexual
behaviors.
f) Cause - The main mode of transmission for the hepatitis A virus is through the fecal-oral
route, whereby an uninfected person consumes contaminated food or water that has
been contaminated with the feces of an infected individual. In familial settings,
transmission can occur through unsanitary hands when an infected person prepares
food for their family members. Although waterborne outbreaks are relatively rare, they
are typically linked to water sources contaminated with sewage or inadequately treated
water. Additionally, close physical contact, such as engaging in oral-anal sex, can also
facilitate the transmission of the virus from an infected person to another individual.
However, it's important to note that casual contact among individuals does not typically
result in the spread of the virus (World Health Organization, 2022).
2. How will you detect this pathogen in food? Design a schema on how you would go about
its detection. Explain your diagram.
To detect HAV from food samples, I will employ the detection method as that of Wu et al. in
2023 for their investigation and rapid detection of HAV from artificially contaminated foods:
a) Inoculation of solid and liquid food samples: HAV suspension in phosphate-buffered
saline (PBS) at different concentrations was evenly pipetted onto the surface of solid
food samples (green onion, strawberry, mussel) or mixed with liquid food (cow milk) in
centrifuge tubes. Uninoculated samples were used as negative controls.
b) Drying and incubation: The inoculated solid food samples were left at room temperature
for 1 hour to allow the HAV to dry onto the surface. The artificially contaminated liquid
or ideally milk, will be mixed well and left at room temperature for 1 hour.
c) Elution of viral particles: The viral particles on the surface of the solid foods is to be
eluted using glycine buffer. The buffer containing HAV particles from the liquid samples
and the eluates from the solid foods will be collected.
d) Concentration of HAV particles: Protamine-coated magnetic nanoparticles (PMNPs) will
be used to capture and concentrate the HAV particles from the liquid samples and the
glycine buffer.
e) RNA extraction: Viral RNA will be extracted from the concentrated samples using a virus
spin kit. The extracted RNA will be eluted in RNase-free water.
f) Quantification of RNA: The extracted RNA is to be quantified using real-time reverse
transcription polymerase chain reaction (RT-PCR) assay
g) Standard curve generation: To establish a standard curve for quantification, HAV RNA
should also be extracted from a known virus stock with a known titer and serially
diluted. Each dilution will be subjected to the same RT-PCR assay.
h) Write conclusion: If the curve shows fluorescence, HAV is present in the food, therefore
appropriate measures should be made to contain and control the possible spread of
infection.
Inoculation of
Solid and Liquid
Food Samples
Drying and
Incubation of
Samples
Elution of Viral
Particles
Concentration
of HAV particles
RNA Extraction
Quantification
of RNA
Standard Curve
Generation
Write-up/Report
Figure 2. Schematic diagram of steps of detection of HAV in artificially inoculated food samples.
References:
Gholizadeh, O., Akbarzadeh, S., Hashemi, M., Gholami, M., Amini, P., Yekanipour, Z.,
Tabatabaie, R., Yasamineh, S., Hosseini, P. & Poortahmasebi, V. (2023). Hepatitis A: Viral
Structure, Classification, Life Cycle, Clinical Symptoms, Diagnosis Error, and Vaccination. Can J
Infect Dis Med Microbiol., . 10.1155/2023/4263309
Gilroy,
R.
(2019,
May
8).
Hepatitis
https://emedicine.medscape.com/article/177484-overview
A.
Emedicine.
Jefferies, M., Rauff, B., Rashid, H., Lam, T. & Rafiq, S. (2018). Update on global epidemiology of
viral hepatitis and preventive strategies. World J Clin Cases., 6(13), 589–599.
10.12998/wjcc.v6.i13.589
World Health Organization, (2022, June 24). Hepatitis A. Who.
Wu, R., Meng, B., Corredig, M. & Griffiths, Mansel W.. (2023). Rapid Detection of Hepatitis A
Virus in Foods Using a Bioluminescent Assay in Real-Time (BART) and Reverse Transcription
Loop-Mediated Isothermal Amplification (RT-LAMP) Technology. Food and Environmental
Virology, volume 15, pages 144–157.