News Scan for Nov 07, 2016

Drug-resistant malaria
;
MERS update
;
Cholera in Yemen
;
Chikungunya outbreak dynamics

Studies identify genetic markers for drug-resistant malaria

Two papers published last week in The Lancet Infectious Diseases describe the identification of molecular markers associated with drug resistance in Plasmodium falciparum malaria.

The two papers were genome-wide association studies of Cambodian strains of P falciparum that were looking to find molecular markers for resistance to piperaquine, a drug that is used in artemisinin combination therapies. As malaria in the Greater Mekong subregion becomes increasingly resistant to artemisinin and the partner drugs that are used to treat the P falciparum parasite—which accounts for most malaria cases and deaths—molecular markers are urgently needed to help public health officials monitor the spread of resistance and recommend alternative treatments.

In addition to Cambodia, artemisinin resistance has been detected in Laos, Myanmar, Thailand, and Vietnam.

In one study, led by researchers from the National Institute of Allergy and Infectious Diseases (NIAID) and the UK's Wellcome Trust Sanger Institute, investigators compared the complete genomes of 297 parasites isolated from Cambodian malaria patients to a reference malaria parasite genome and identified two genetic markers—amplifications of the exo-E425G and plasmepsin 2 and 3 genes—associated with the parasites' ability to resist piperaquine. The researchers believe that the amplification of the plasmepsin 2 and 3 genes may play a functional role in enabling parasites to resist piperaquine.

In the other study, researchers from the Institut Pasteur in Cambodia did a gene-wide association study on 31 malaria strains to define the resistant in-vitro phenotype. They found that an increased plasmepin 2 gene copy number was strongly associated with dihydroartemisinin-piperaquine treatment failure.

"The converging results of these studies make plasmepsin 2–3 amplification a robust marker for piperaquine resistance in the region," an accompanying commentary notes. "P falciparum transfected with multicopy plasmepsin 2–3 will be an invaluable tool to explore underlying resistance mechanisms."

Information about the distribution of these drug resistance markers, a press release from NIAID explains, is being used by officials in Cambodia and neighboring countries to determine the spread of piperaquine resistance and help guide treatment approaches.
Nov 3 Lancet Infect Dis study
Nov 3 Lancet Infect Dis
study
Nov 3 Lancet Infect Dis
commentary
Nov 3 NIAID
press release

 

Saudi Arabia reports new MERS cases

The Saudi Arabian Ministry of Health (MOH) reported two new cases of Middle East respiratory syndrome coronavirus (MERS-CoV) yesterday and today.

On Sunday, the MOH said a 52-year-old man from Bahrah was in critical condition after presenting with symptoms of MERS-CoV. The man had direct contact with camels. Though experts aren't clear on the route of transmission, exposure to camels (including drinking raw camel milk) is a known risk factor for MERS-CoV.

Today a 58-year-old expatriate woman from Najran was listed in stable condition after presenting with symptoms of MERS. She is listed as a primary source of infection, which means she did not contract the virus from someone else.

Confirmation of the latest infections raises Saudi Arabia's MERS-CoV total to 1,475 cases, 615 of them fatal. Seven people are still being treated for their infections, after a 51-year-old Saudi woman from Kharj made a recovery over the weekend.
Nov 6 MOH update
Nov 7 MOH update

 

WHO: More cholera in Yemen

The World Health Organization (WHO) released an update on the current cholera outbreak in Yemen yesterday, reporting that there were now 2,733 suspected cases and 51 deaths from the disease. The last update on Oct 27 reported 1,410 suspected cases and 6 deaths. 

While only 75 cases of cholera have been laboratory confirmed, several governorates in the Middle Eastern country are reporting cholera, including Ta’iz, Aden, Lahij, Al Hudaydah, Hajjah, Sana'a, Al Bayda, Dhamar, and Ibb.

The current outbreak began in early October, and on Oct 28, the WHO gave Yemen $1 million in emergency funds to fight the spread of the illness, which causes acute watery diarrhea. Cholera is endemic in Yemen, but the current outbreak has been made worse by crumbling public health infrastructure and surveillance. Almost 8 million people are currently living in areas affected by the outbreak, including 3 million internally displaced persons.
 Nov 6 WHO update

                               

Home exposure a risk factor in chikungunya outbreaks

Chikungunya outbreaks seem to be fueled by infections in and around the home, with women more likely to get sick, according to a study today that focused on a small rural village in Bangladesh. Researchers from the Johns Hopkins Bloomberg School of Public Health, the Pasteur Institute, and their partners in Bangladesh reported their findings in the latest edition of Proceedings of the National Academy of Sciences (PNAS).

The team analyzed who did and didn't get sick in a 2012 chikungunya outbreak in a village about 60 miles outside of the capital city Dhaka. They visited every household, interviewing 1,933 people from 460 households. Eighteen percent (364) of the residents had symptoms consistent with the disease.

Though the virus is spread by mosquitoes, researchers found that more than a quarter of the cases occurred in households less than 200 meters apart, making up small clusters, which the researchers said was an unexpected finding.

When they examined movement patterns in the Bangladeshi population they found that women spent 66% of their time at home between 8 a.m. and 8 p.m., while men spent 45% of their time at home. Given that the mosquitoes carrying chikungunya virus don't travel far, being at home was a risk factor for infections during outbreak settings.

Henrik Salje, PhD, with the department of epidemiology at Johns Hopkins, said in a press release from the school that mosquitoes appear to be very lazy. "They bite someone in a household and get infected with a virus and then hang around to bit someone else in the same home of very nearby."

Though there are few tools for battling mosquito-borne disease such as chikungunya and Zika virus, the authors said the study findings could help target interventions, especially to people who spend most of their time in and around their homes.
Nov 7 PNAS report
Nov 7 Johns Hopkins
press release

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