New research presented at the 2016 America Society of Tropical Medicine and Hygiene annual meeting found mosquitoes can carry more than one flavivirus at a time, enabling them to potentially infect humans with Zika and chikungunya viruses in a single bite.
“There was a large-scale study recently in Nicaragua where they found that over 20% of the patients that have one arbovirus actually were coinfected with another one, so we figured there must be a reasonable number of mosquitos that actually are exposed to two viruses at the same time,” Claudia Rückert, PhD, virology researcher from Colorado State University, told Infectious Disease News. “We want to know, can a mosquito transmit two viruses at the same time, and how are the dynamics of virus infection changed by the presence of another virus?”
‘Subtle interactions’ between mosquitoes, viruses
Zika’s possible interactions with chikungunya are mostly unknown in mosquitoes. In a contained experiment, Rückert and colleagues had Aedes aegypti and Aedes albopictus mosquitos feed on blood that contained dengue, chikungunya and Zika, either in combination or alone.
The researchers found that the mosquito’s saliva tested positive for Zika and chikungunya, confirming that mosquitos can carry both viruses simultaneously. Rückert and colleagues also suggest that one virus may outcompete another in mosquitoes, which impacts the epidemiology of two mosquito-borne viruses circulating simultaneously.
However, whether mosquitos can pick up all three viruses simultaneously is still uncertain.
“There’s a lot of subtle interactions that seem to occur between the viruses and the mosquitoes,” Rückert added. “We have mosquitos that can transmit chikungunya and Zika at the same time, you can get mosquitoes that can transmit dengue and Zika at the same time, and dengue and chikungunya. All three combinations of those viruses can be transmitted by one mosquito.”
Flavivirus infections linked with neurological problems
In a second study presented at ASTMTH 2016, researchers in Brazil associated each disease —dengue, chikungunya and Zika — with severe neurological problems.
Study researcher Mateus Santana do Rosário, MD, evaluates a patient with Guillian-Barré syndrome at Roberto Santos Hospital, Brazil.
Source: Isadora Siqueira
Isadora Cristina de Siqueira, PhD, researcher at the Public Health Research Center Gonçalo Moniz, Fundação Oswaldo Cruz in Brazil, and colleagues encountered neurological issues in a group of 21 patients at the Roberto Santos General Hospital in Salvador, Brazil, during an outbreak of the three viruses in 2015.
“[We] started this study at the very beginning of the Zika outbreak with the intention to start surveillance for possible cases of Guillain-Barré syndrome associated with Zika virus infection and characterize the clinical presentation of the cases,” Siqueira told Infectious Disease News.
The researchers observed opsoclonus-myoclonus-ataxia syndrome (OMS) in two patients, both of whom were coinfected with either chikungunya and dengue or Zika and dengue. This unusual diagnosis of OMS prompted the investigators to consider whether the problem resulted from an autoimmune disorder triggered by one of the viruses that caused the immune system to attack nerve cells, similar to what occurs in Zika patients who develop Guillain-Barre syndrome (GBS). They suggest GBS is not exclusively caused by Zika, and may occur in patients with chikungunya or dengue as well.
Due to the similarities between dengue and Zika, Siqueira and colleagues believe the presence of dengue antibodies may affect the course of Zika infection in patients. They referenced the Brazilian outbreak of Zika in 2015, which left many people who had previous dengue infections susceptible to more severe disease.
“Besides GBS, we also identified cases of encephalitis, [acute disseminated encephalomyelitis] and OMS, a rare syndrome characterized by chaotic eye movement and ataxia,” Siqueira added. “Clinicians and health care providers should be aware of the potential severe neurological complications associated with Zika, chikungunya and dengue virus infection in epidemic areas.”– by Savannah Demko
Siqueira IC, et al. Abstract LB-5422. Presented at: American Society of Tropical Medicine and Hygiene annual conference; Nov. 13-17, 2016; Atlanta.
Rückert C, et al. Abstract 608. Presented at: American Society of Tropical Medicine and Hygiene annual conference; Nov. 13-17, 2016; Atlanta.
Disclosure: The researchers report no relevant financial disclosures.