Effective Population Size Differences in Calomys musculinus, the Host of Junín Virus: Their Relationship with the Epidemiological History of Argentine Hemorrhagic Fever

Abstract

Argentine hemorrhagic fever (AHF) is a serious endemic disease in Argentina, produced by Junín virus, whose host is the Sigmodontinae rodent . Within the endemic area, human incidence and proportion of infected rodents remains high for 5-10 years after the first appearance of the disease (epidemic [E] zone) and then gradually declines to sporadic cases (historic [H] zone). We tested the hypothesis that host populations within the E zone are large and well connected by gene flow, facilitating the transmission and maintenance of the virus, whereas those in the H and nonendemic (NE) zones are small and isolated, with the opposite effect. We estimated parameters affected by levels of gene flow and population size in 14 populations of: population effective size (), genetic variability, and mean relatedness. Our hypothesis was not supported: the lowest levels of variability and of and the highest genetic relatedness among individuals were found in the H zone. Populations from the NE zone displayed opposite results, whereas those in the E zone showed intermediate values. If we consider that populations are first NE, then E, and finally H, a correlative decrease in was observed. Chronically infected females have a low reproductive success. We propose that this would lower because each cohort would originate from a fraction of females of the previous generation, and affect other factors such as proportion of individuals that develop acute infection, probability of viral transmission, and evolution of virulence, which would explain, at least partly, the changing incidence of AHF.

A Review of Mammarenaviruses and Rodent Reservoirs in the Americas

“…For example, Mills et al ( 1992 ) associated low temperatures to low resource availability, because of decreased rain. In turn, sites with temperate climates, less temperature variations and more rain accommodate a larger diversity of rodents, as well higher abundance of Calomys musculinus (Mills and Childs 1998 ; Chiappero et al 2018 ).…”

Recent developments on Junin virus, a causative agent for Argentine haemorrhagic fever

“…The rodents with the highest population density are considered the main reservoir of the virus. Due to high population density, the principal rodent reservoir is Clomys musculinus , a member of the Muridae family and Sigmodontinae subfamily 21 . Some of these infected rodents suffer from acute diseases and with the antibody response, remove the virus from their body while other rodents develop a persistent infection and shed off the virus via urine, saliva, and faeces for a long term 22 .…”

“…26 A rationale hypothetical genetic study in rodent acting as a host performed by Chiappero et al indicates the dynamics of the expansion and changing incidence of AHF. 21 The chances of infection were four times more in males as compared to females because occupationally, males were more frequently exposed to rodent reservoirs than females. The infection is 90% more widespread in the rural population than in the urban population.…”

“…Due to high population density, the principal rodent reservoir is Clomys musculinus, a member of the Muridae family and Sigmodontinae subfamily. 21 Some of these infected rodents suffer from acute diseases and with the antibody response, remove the virus from their body while other rodents develop a persistent infection and shed off the virus via urine, saliva, and faeces for a long term. 22 The spread of the Junin virus in Clomys musculinus is horizontal as well as vertical that is, it spreads in rodents of the same generation during aggressive encounters among the adult rodents to defend their territory and from the mothers to their offspring.…”

“…A rationale hypothetical genetic study in rodent acting as a host performed by Chiappero et al. indicates the dynamics of the expansion and changing incidence of AHF 21 …”