@turquoise-- As far as I know, there are two types of leishmaniasis viruses. One is cutaneous which occurs on the skin and the other is internal which is what causes black fever.
So not everyone who gets infected with leishmaniasis will develop black fever. But black fever is definitely way more dangerous than cutaneous leishmaniasis which is easily treatable. Although both have complications if they're not diagnosed early on.
If there is a threat of leishmaniasis for pets in the US, it's most likely cutaneous. And I don't think that cutaneous nor black fever is a threat for people in North America.