Argentina's 2028-maturing, euro-denominated bond was down nearly 9 cents in European trading Tradeweb data showed.
Fernandez's lead far exceeded the margin of 2-8 percentage points forecast in recent opinion polls.
Happy and excited about the results of the primary elections, presidential candidate Alberto Fernandez said that "A new Argentina is being born, " and another history is beginning to be written. The Global X MSCI Argentina ETF was down more than 22% in premarket trade Monday.
The markets have little faith in Fernandez, who is widely seen as dependent on Kirchner, but that made scant difference to voters.
"I would say they (bonds) are pricing in a much higher probability of a default", said Aberdeen Standard EM portfolio manager Viktor Szabo.
"Given the narrow path ahead, our view is that a high degree of policy continuity is a must in order to maintain macro stability", Morgan Stanley said in a research note.
Macri has convened a government meeting after losing Sunday primaries and ordered the ministers to analyze the necessary changes in governance and develop a strategy to prevent a sharp fall in the rate of the national currency.
"Another sharp and sustained episode of financial volatility that interrupts the recent downward trend in inflation, improvement in confidence and recovery in economic activity could increase voter frustration with Macri and lead his support to erode from current levels".
An acute financial crisis previous year hit the peso and forced Macri to take the International Monetary Fund loan in return for pledging to balance Argentina's deficit.
The preliminary results from Sunday's voting suggest the conservative Macri will face an uphill battle going into general elections in October and it sent Argentina's stocks, peso and bonds tumbling over concern at a return of the populist governments that preceded him.More news: Albon replaces Gasly at Red Bull from Spa
More news: Multiple People Reportedly Stabbed In Sydney's CBD
More news: Jeffrey Epstein Autopsy Results ‘Pending Further Information’ Following Examination
Argentina's main political parties had already chosen their presidential nominees, allowing the primary to serve as a first concrete measure of voter sentiment.
Emerging market currencies feel pressured as USD/ARS adds more than 30%.
Markets panicked as the peso closed at 57.30 to the dollar, a drop of 18.76 per cent from its Friday closing figure, while the Merval index crashed 38 percent by close..
Fernandez said the market reactions were in response to Macri's failures on the economy. "The markets are giving warning that the government has put itself in a position it can not respond to", Fernandez told Radio 10 on Monday.
Voters were given a stark choice: stay the course of painful austerity measures under Macri or a return to interventionist economics.
Cristina Fernandez is now facing a series of trials for corruption during her 2007-2015 administration. She feuded with the country's key farm sector over export taxes and presided over a multi-year standoff with bondholders that kept Argentina locked out of the global capital markets.
Sunday's primaries were seen as vindication for "Kirchnerismo" which have for years denounced Mr Macri's plan as ineffective.
"We had a bad election", Macri told supporters in Buenos Aires even before official data was released.
Macri's election in 2015 marked the first time in a more than a decade that Argentina's centre-right opposition had unseated the centre-left Peronist movement to which Cristina Fernandez belongs.