Could Zika be the Mysterious Killer of Howler Monkeys in Nicaragua?

Scientists are concerned that the recent mysterious deaths of howler monkeys in Nicaragua could be a result of the Zika Virus. Recently, nearly 40 howler monkeys have been found dead in the tropical region, with no apparent signs of trauma [1].

Paso Pacifico, an environmental non-profit organization that works in the Pacific jungles of Central America, is leading the efforts to determine what the cause of death is for these monkeys.

The howler monkey is a New World Monkey found in tropical Central and South America, and is well known for its harsh and stinging cries. [2].

Kim Williams-Guillen, a conservation researcher, who has been researching in Nicaragua’s jungles since 1999, told the Global Post, “Wild animals die off all the time, but it is really unusual to see this many deaths in such a short time with no apparent reason…I have never seen anything like it” [3].

The Zika virus, a flavivirus carried by the Aedes aegypti mosquito, has been rapidly spreading throughout South and Central America. Its surge in human cases within recent months have led experts to question whether it may play a role in the mysterious die-off of the tropical monkeys. While Zika virus is a suspected cause of the recent surge in deaths of howler monkeys, a confirmed direct link remains quite unclear Both Zika virus and Chikungunya are vector-borne diseases carried by the same mosquito that carries Dengue and are relatively new to the Western Hemisphere. There is relatively little research published on the effects of Zika and Chikungunya in humans, let alone in the wild monkey population, who are infected via the mosquito just as humans are. Nicaragua has reported 29 cases of Zika in humans so far, and approximately 100,000 cases of Chikungunya since 2014. However, it has not yet been researched how either of these diseases affect primates [1].

What we do know is that howler monkeys are immune to dengue, but are highly susceptible to yellow fever [1]. Yellow fever causes mild symptoms in most species of Old World monkeys, while it can cause severe illness in New World monkeys [4]. Scientists think the high susceptibility may be related to the lack of co-evolution with the virus [5]. Yellow fever has been eradicated from Nicaragua since 1954 [6]. However, between 2007 and 2008, Northeastern Argentina faced a major yellow fever outbreak that led to the death of 59 howler monkeys. This yellow fever outbreak held significance to public health research because it emphasized the interconnectedness between human and animal health [5]. Zika virus, also newly introduced to Americas, was first detected in a feverish rhesus monkey, a species of Old World monkeys, in Uganda in 1947 [7]. Further research regarding susceptibility of New World wild animals to Zika virus will help both conservation of wild life and future public health strategy to fight against Zika virus.

Paso Pacifico is now working with scientists at University of California at Davis to determine the cause of death for the howler monkeys in Nicaragua. [1]. If the link to Zika and the death of howler monkeys in Nicaragua is confirmed, it could be a sentinel signal or precursor to the spread of disease in humans. What experts are hoping to determine is how Zika virus could affect the species or other potential determinants of the unusual die-off of the monkey.

The World Health Organization declared Zika virus a Public Health Emergency of International Concern on February 1^st, 2016. On Wednesday, February 17^th, 2016 the WHO released a Strategic Response Framework for the spread of Zika virus [8,9].

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