micro sheet # 10

Micro 10th lec.
Date: 1/3/2011
Done By: isra'a drarjeh

** Measles (Morbillivirus)
It's called Morbillivirus in relation that this disease can be so sever and dangerous to the infected person.
Measles virus is part of the respiratory viruses in relation to the root of infection (the infection start in the respiratory tract) and in the form of acute respiratory tract infection.
It causes Rash that starts in any part of the body but mainly on the trunk and the face and other parts of the body.
The infection associated with minor number of lesion for erythematic and may spread over the surface of the body.
This virus to some extend related to Paramoxyvirus in many feature.
It contains specific receptor in forms of spikes, hemagglutinin carried on one spike, in the second spike there is a layer of F-protein that responsible for the fusion of the virus with the infected cell membrane.
F-protein in measles has an addition function  produce hemolysin in relation to RBC's especially in vitro can be demonstrated and also recognized in clinical feature of the disease which affect the small bld vessels and produce erythema rashes.
M-protein  contribute for invasion of the virus in the cytoplasmic of the infected cells.
Incubation period between 1 to 2 weeks, the virus requires this period to replicate and produce sufficient amount of viruses in order to produce what's called the clinical feature of the disease.
In contrast to Parainfluenza viruses, this virus is managed to reach the bld stream and once it reaches the bld stream in sufficient amount it causes what's called "primary virema", later on it transmits to the reticuloendothelial system and also the lymph system and retains back to the bld stream to produce "secondary virema" which associated with the clinical feature of the disease, there for the incubation period between starting of the infection and developing of the disease require as you see 1-2 weeks.
So children (children are more susceptible) may suffer at the beginning of a mild respiratory tract infection but later following the replication of the virus in bld stream by primary and secondary associated with clinical feature of the disease.
Clinical feature : at the beginning might misdiagnosed as flu-like disease but less sever cause there is a mild sore and congestion in the throat mucosa, mild or high fever, cough, running nose.
The most important clinical feature  the virus reaches the bld stream and produce virema and leukepenia which indicate that it reaches the maximum of multiplication and often associated with skin rash in any part of the body, might start on the trunk or the face and it will spread over the surface of the body.
The rash will disappear after 1 week if there is no manipulation of the rash.
Children will get allergic reaction and some burning sensation and they try to relive themselves by using their fingers  produce secondary skin infection and damage to the skin in some cases. In such a care the only way to reduce the body temperature of the infected child by using medicament or warm water to wash his body and using certain powder in order to reduce the sensitivity sensation in the skin otherwise he might suffer from some skin injuries and secondary bacterial infection.
Complication: normally 90% manage to develop clinical feature without any complication, 10% might developing some complication.
The complication related to respiratory tract in form of bronchitis, bronchopneumonia, it might be associated with signs and symptoms related to the stomach and intestine in the form of diarrhea. There are some complication related to the oral cavity  stomatitis and Koplick's spot  small irregular spots erupted on the oral cavity especially near the molar teeth and often it's not so serious.
There might be activation of some type of bacteria that will cause otitis media or diarrhea due to the presence of toxic E.coli or encephalitis, it rare reach meninges and cause encephalomeningitis.
The complication mainly results in  multiple sclerosis which affects the myelin layer of the brain and spinal cord and prevents the connection between them.
In relation to the intestine  it might produce intestinal inflammation known as "Krauze disease" it's a form of chronic inflammatory reaction in the mucosa of the large intestine occur specially in children and they will suffer from continues diarrhea, constipation and abdominal pain.
These complications occur in few percentages especially in children who have immunodeficiency.
The most dangerous complication  post measles encephalitis which affects the brain causing minor damage, it also affects the lung causing giant cell pneumonia. And this recognized in elderly children and adult more than young children.
In general we divide children to 2 parts: young up to 12 years when infected with measles virus the end result is harmless and developing of immunity. Children > 12 or suffer from malnutrition and vitamin A deficiency the infection can be so fetal and associated with many complication  encephalitis, multiply sclerosis, pneumonia, ulceration in the cornea causing blindness.
Fatality might reach in such type of person up to 20 % especially in under developing country.
Infection of measles under natural condition always resulted in developing of permanent immunity, there is no reinfection.
Measles mumps Rubella vaccination (MMR) is recommended to be given in 2 doses: 1st  9-12 months bending that the child is free of respiratory tract infection and fever. 2nd 4-5 years before the children enter the elementary school.
Diagnose: there's a test which demonstrated the presence of specific antibody in form of igG and igM in bld and saliva.

** Respiratory syncytias virus (RSV)
Syncytias  due to the fact that this virus induces enlargement of the infected cells in the tissue culture.
RSV classified as part of paramyxovirus but recently they have separated this virus and included in another group called pneumovirus group, due to the fact that it always associated with lower respiratory tract infection.(it starts in the upper R.T and then spread to lower R.T).
The morphology of this virus is similar to other paramyxoviruses except that there is no HA and NA antigens instead there is another layer (surface antigen) known as G-glycoprotein that has the same role  attach to the surface of the mucosa of the R.T. cells by presence of specific receptor (salicylic acid receptor) and F-protein.
F-protein in this virus has an addition function to that induce the enlargement in the infected tissue, so F-protein responsible for fusion of the virus and induce enlargement of the infected tissue, but it's less recognized in vivo than in vitro.
RSV composed of one major type and 2 subtypes (A and B) but they are similar.
RSV is less resistance to environmental factors. It can be easily killed after few minutes when get out the body by cough and sneezing, there for most cases of infection are due to direct close contact (saliva, nasal mucosa) only, not by inhalation from environment.
The infection often recognized more commonly in winter season, it can't survive in high temperature.
It might produce infection in certain animals like cattle, sheep and goat.
Generally RSV related to the upper R.T at the beginning of infection produce what's called mild upper R.T infection but often in the lower R.T and often the infection common among infant (few weeks – 1 year).
Researchers in our country have done a study and they found that the majority of children have been exposed to RSV.
RSV Infection are more dangerous in adult and elderly specially in immunocompromised person and associated with many complications (pneumonia, secondary bacterial pneumonia, severe asthma specially in elderly)
It's considered as opportunistic pathogen in immunocompromised person and who treated with anti-cancer drugs …etc.
Treatment: Ribavirin (anti-viral) not always effective in treating the infection… there is no specific antiviral treatment.
Lab diagnose: there is a test that can be done easily in the lab by immunological method like (ELISA) to detect if the infected person is infected with RSV or not or if there is a specific antibody or not.
Immunity followed not from the first infection, so more one time of infection makes immunity.
There's a new effective vaccination for RSV but it still under trail.
The supportive therapy is the choice for treatment of adult and elderly hospitalized patient.
The only way to prevent the spread of the disease in the hospitalized environment is to have a good hygiene practice.

** Human Meta Pneumovirus virus (HMPV)
It's newly discovered, it might be part of the RSV might during mutation resulting in such a form, it has the same morphologic structure and the same mechanism of infection of RSV and Rhinovirus.
It affects the same age group of children of RSV but it's more severing in some cases associated with bronchitis and pneumonia.
The only important feature of HMPV  affects directly the lower respiratory tract (Remember that RSV and parainfluenza virus start mainly in the upper respiratory tract) there for HMPV is associated with pneumonia more than other viruses.
There is no vaccination available, only supportive therapy and preventing the dissemination.
HMPV has been recognized in our country but RSV is more common.

** Picorneviruse
Picorne  mean originated from very small size virus.
This group is complex; include many important human pathogenic viruses in relation to the R.T and intestinal tract.
There are certain Picornaviruses that cause only R.T infection and other produce R.T infection but later reaching the intestinal tract and began to produce infection in the intestine and might spread to the bld produce virema and the central nervous system and meanings produce encephalomeningitis specially the group which called Entroviruses.
Rhinoviruses  related to the mucosa of the nose produce infection in the mucosa of the nasal cavity and it might also infect the larynx and the lung.
Rhinoviruses are not susceptible to the acidity of the stomach.
Entroviruses  the root of infection might be directly to the R.T or the intestine tract by consumption of food and water or by direct contact reaching the stomach and the intestine.
It multiply in the R.T mucosa and later reach the intestine and the bld and from the bld to the intestine again … more complex.
It's a large group include (71-75 viruses) and each of these viruses associated with some type of infection.
The most common  polioviruses the causative agent of poliolitis, chchoriviruses, coxasakiviruses {very common} produce a different type of infection beginning from ulceration in the oral cavity to intestinal infection related to diarrhea and other inflammation, it might reach the bld and meninges produce meningitis and encephalomeningitis.
There is another imp. Animal virus known as foot and mucosa disease virus, it's mainly affecting the large animal like cattle, horses and camels. Very dangerous virus and might produce infection in human.
Features of picorneaviruses  Not enveloped, +ve single strand RNA, in relation to the surface antigen it has a special projected antigen which composed of different polypeptide, generally there are 4 types (VP1-VP4) these polypeptides responsible for the interaction with the mucosa of the R.T and the intestinal tract.
Most Picornaviruses specially entroviruses consider highly stable in the nature (water, soil) and survive in the acidity of the stomach, the virus can be detected in the feces of the infected person.