Prevalence of Plasmodium Species among Humans and Monkeys at Mole National Park in Northern Ghana

Review Article

Austin Environ Sci. 2022; 7(1): 1070.

Prevalence of Plasmodium Species among Humans and Monkeys at Mole National Park in Northern Ghana

Dadzie E1, Rebecca EM1, Quaye L2, Helegbe G3, Ziekah MY4, Abubakari BB5, Aniweh Y6 and Abdul-Karim A7*

1School of Medical Laboratory Science, UDS, Ghana

2College of Allied Health Sciences, UDS, Tamale, Ghana

3School of Medicine, UDS, Ghana

4Department of Game and Wildlife, Ghana

5Regional Health Directorate, Tamale, Ghana

6West African Centre for Cell Biology of Infectious Pathogens, Ghana

7Public Health Laboratory, Tamale, Ghana

*Corresponding author: Abass Abdul-Karim, Public Health Laboratory, Tamale, Ghana

Received: December 08, 2021; Accepted: January 24, 2022; Published: January 31, 2022


Malaria is one of the most severe public health problems in Ghana. In developing countries such as Ghana, with high of prevalence of malaria, the procedures for diagnoses and detection is limited in technological depth and for that reason most of these parasites; Plasmodium ovale, Plasmodium malariae, Plasmodium vivax and Plasmodium knowlesi are not routinely screened for; as such this study seeks to determine the prevalence of Plasmodium species among humans and monkeys at Mole National Park in Northern Ghana.

A total sample size of 217 comprising 214 human subjects and 3 baboons were recruited in this study conducted at Mole National Park. Data including; age, marital status, gender, occupation, knowledge on malaria and educational background information were collected. Blood samples were taken from both humans and baboons for the malaria testing using RDT, Microscopy and PCR to detect Plasmodium falciparum, Plasmodium ovale, Plasmodium malariae, Plasmodium vivax and Plasmodium knowlesi.

The mean age of the study participants was 24.2±15.2. All the 3 baboon subjects were negative on RDT but one (1) out of the three was positive on microscopy. That notwithstanding, the same microscopy positive baboon subject was Pan-Plasmodium positive on PCR but was negative for the tested Plasmodium falciparum, Plasmodium ovale and Plasmodium malariae.

The study recorded prevalence of plasmodium species using RDT and microscopy respectively to be 22.9% and 18.2%. The prevalence of Plasmodium falciparum, Plasmodium ovale and

Plasmodium malariae among the human participants from this study were 39.9%, 12.6% and 18.6% respectively. Mixed infections were identified in 7.5% of the human participants where 4.2% was Plasmodium falciparum/Plasmodium ovale, 2.8% was falciparum/malariae mixed infection and 0.5% malariae/ovale mixed infection.

Sociodemographics, knowledge on malaria and interaction with monkeys of study participants did not show any significant association with malaria infection.

Prevalence of malaria parasites was high among the participant, which poses threat to reduction of malaria in the country.

Keywords: Malaria; Ghana; Outpatient departments; Monkeys; Plasmodium ovale


Malaria infection in humans is caused by five plasmodium species: Plasmodium falciparum, Plasmodium ovale, Plasmodium vivax, Plasmodium malariae and Plasmodium knowlesi. Among the five human plasmodium parasites, Plasmodium falciparum causes more than 90% of the world recorded malaria morbidity and mortality four of the plasmodium species: Plasmodium falciparum, Plasmodium ovale, Plasmodium vivax and Plasmodium malariae are transmitted from one person to another by the bite of an infected female anopheline mosquito [1]. The fifth malaria parasite, Plasmodium knowlesi is a simian malaria parasite predominantly found in Southeast Asia. Zoonotic transmission of Plasmodium knowlesi malaria occurs following the bite of an infected female anopheles mosquito (Anopheles Leucosphyrus and Anopheles latens) which results in severe diseases, high mortality in infant, children and in naïve adults Wesolowski et al., [2].

Ghana is a malaria endemic country with the entire population being at risk of malaria infection. Children below 5 years of age as well as pregnant women are at a higher risk of malaria infection due to lowered immunity. Presumptively, malaria cases reported at the Outpatient Departments (OPD) was 37.5% in 2015 [3]. Over the years, malaria morbidity and mortality have been reported to be declining in Ghana due to the implementation of various policies by the Ministry of Health and the Ghana Health Service including the use of Sulfadoxine-Pyrimethamine (IPTp-SP) as an intermittent preventive treatment in pregnant women, the free distribution of insecticide treated net and diagnostic based approach with RDT, microscopy or PCR analysis before patient treatment [4,5].

In Ghana, Plasmodium falciparum causes about 90% of all malaria infection followed by Plasmodium malariae which causes less than 10% and more rarely Plasmodium ovale which causes about 0.15%. Plasmodium vivax and Plasmodium knowlesi have been reported to be absent in the country [3]. Anopheline gambiae species complex and Anopheline funestus are the major types of female anopheline mosquitoes that transmit the plasmodium parasites. Anopheles melas is found in the mangrove swamps of the southwest while Anoheline arabiensis in savannah areas of northern Ghana [3]. Despite the availability of effective antimalarial agents Hommerich et al., [4], failure to make the correct diagnosis has resulted in inappropriate therapy leading to preventable deaths.

The use of molecular tools for the detection of plasmodium parasite has deepened the epidemiology of malaria and highlighted plasmodium parasite infection in humans. A retrospective study conducted by using Polymerase Chain Reaction (PCR) on already examined Plasmodium malariae slide showed that 97% of the slides tested positive for Plasmodium knowlesi with only one being positive for Plasmodium malariae. The use of molecular biological technique has significantly impacted and facilitated the identification of infections caused by Plasmodium falciparum, other plasmodium species and mixed infections.


Globally, malaria remains a significant infectious disease causing about 584,000 deaths and leads to an estimated 198 million cases in humans annually [6]. Statistics from 2015 to 2017 shows no significant reduction in global malaria cases. 219 million cases and 435,000 related deaths were recorded in 2017 about half of the world populations live in malaria risk areas. The annual malaria associated mortality approaches 1 million globally, with two (2) children dying from the disease every minute [7].

The protozoan parasite belonging to the genus Plasmodium causes malaria in humans. More than 150 plasmodium species have been identified to cause malaria in mammals, birds and reptiles [8]. Malaria parasite tends to be host specific regardless of having large number of hosts.

The natural host for the four (4) Plasmodium species; Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale is human whereas long-tailed macaques (Macaca fascicularis) and pig-tailed macaque (Macaca nemestrina) are hosts for five (5) Plasmodium species: Plasmodium knowlesi, Plasmodium fieldi, Plasmodium coatneyi, Plasmodium cynomolgi, and Plasmodium inui.

Even though the four species of Plasmodium parasite exploit humans as intermediate hosts, at least more than twenty-six additional Non-Human Primate (NHP) parasites exist outside Homo sapiens hosts [9]. The principal record of NHP malaria parasite was reported by in an orangutan, Pongo pygmaeus. Plasmodium pitheci species was described a few years later, alongside Plasmodium inui and Plasmodium cynomolgi that infect sympatric monkey species, Macaca fascicularis and Macaca nemestrina, in Borneo [10].

Primate malaria discoveries continued as parasitologists investigated an increasing diversity of apes, monkeys, and lemurs from across the world. The infection of human with monkey malaria in 1965 by Chin et al., [11] initiated a resurgence of NHP malaria research focused on Southeast Asia, resulting in nine newly reported malaria species in Asian apes and monkeys a review paper by Vythilingam, [12] reported that is first discovered malaria parasite in long-tailed macaques. The parasite was again identified by Knowles and Das Gupta in long-tailed monkey that was migrated from Singapore to Calcutta [13].

Epidemiology of Plasmodium Species

Geographic distribution

Malaria is a mosquito borne disease in humans and animals following the bite of infected anopheline mosquito [14]. Parasitic protozoan of the genus Plasmodium causes malaria in human [15]. The mosquitoes, which act as vector for this disease, are female Anopheles funestus, Anopheles moucheti, Anopheles gambiae and Anopheles arabiensis [1].

Plasmodium knowlesi has been reported to be absent in Africa and for that matter Ghana as there are no investigations that have proof of endemic transmission but recently, increase in deforestation has cause many monkeys to have close contact with humans. In wild life reserved areas such as Mole National Park in Ghana, monkeys especially the baboon usually find food in neighboring human habitat which may lead to possible zoonotic transmission.

Reservoir hosts

Humans are the natural reservoir host of the four common malaria parasites: Plasmodium falciparum, Plasmodium ovale, Plasmodium malariae and Plasmodium vivax while distinctive hosts of Plasmodium knowlesi identified were long-tailed (Macaca fascicularis) and pig-tailed (Macaca nemestrina) macaques from Singapore [13]. Zoonotic transmission occurs in humans living close to these macaques as reported in Southeast Asia [2,16-19].

Morbidity and mortality

As indicated by World Health Organization (WHO), malaria accounts for about 219 million cases and an expected 1 million deaths per annum a 2014 report by WHO Africa indicates that in every minute a child living in Africa dies from malaria infection [6]. In 2015, Ghana recorded about 10 million suspected malaria cases with 31% being children under 5 years of age [3]. Within that same period, 7% of all mortality were attributed to malaria with 48.4% deaths being children under 5 years. Meanwhile mortality have declined significantly from 12.3% since 2011 to 4.2% in 2016 [3] due to improved health systems, financial aids from international organizations and strategic plans such as the Presidents Malaria Initiative and National Malaria Control Program [3].


Vectors and mode of transmission: Humans becomes infected with malaria parasite following the bite of infected female anopheline mosquitoes. More than 30 species of the mosquito vectors have been described to transmit malaria parasite [1]. These mosquitoes usually bite at dusk and at night which is the most active feeding times for the vectors the mosquito is infected following the bite of an infected human where it sucks the male and female gametocytes. The gametocytes continue the sexual phase of the cycle and the sporozoites fill the salivary glands of the infested mosquito humans can also be infected by contaminated blood in rare cases. Vertical transmission of plasmodium species can also occur during delivery (congenital malaria). Blood transfusion, organ transplant or shared use of needles can be a risk of malaria transmission since malaria parasite normally feed on red blood cells. [20].

Hypothetically, four modes of malaria transmission have been identified: from an infected monkey to another monkey, from an infected monkey to human, from an infected human to another human and from an infected human back to monkey.

Risk factors for Plasmodium species transmission: Genetic factors of an individual from birth pose a risk of malaria infection. Two genetic factors have been linked with the red blood cell, which are of epidemiological importance. People with sickle cell traits are relatively protected from falciparum malaria infection. The sickle cell traits are commonly found in Africa where malaria is endemic and is thought to provide protection from malaria infection [21]. Duffy antigen has been reported to be the invasion point for Plasmodium vivax and Plasmodium knowlesi in humans the presence of the Duffy antigen on the surface of the erythrocyte increases the susceptibility to vivax and knowlesi malaria and it is believed that Duffy antigen acts as a receptor for attachment of plasmodium merozoites majority of Africans especially West Africans are Duffy negative and therefore are resistant to Plasmodium vivax and Plasmodium knowlesi infection [21]. Previous repeated malaria infection may lead to the development of acquired immunity against malaria and subsequent malaria infection may not develop severe complications and may lack typical malaria symptoms [21]. Pregnancy increases susceptibility to malaria. Pregnant women who have had immunity against malaria may lose this immunity especially in their first or second pregnancy [21].

Human behavior may pose a risk to malaria infection. Forest exposures, poor rural population in endemic areas, uneducated individuals, travelers from non-endemic area to endemic area are factors associated with malaria infection. Human activities may create site for mosquito breeding such as standing waters in irrigation ditches, burrow pits, etc [21].

For all vector-borne infections, the transmission is highly based on the bionomics of the vector in question. For example, because Anopheline arabiensis is an outdoor resting dominant vector species Hay et al., [22] people who work outdoors are at risk of contracting malaria by this vector.

Life Cycle of Plasmodium Species

Malaria parasites life cycles in humans and other primates begin when an infected female anopheline mosquito inoculates sporozoites into the bloodstream of its host while feeding on the blood [8].

Sporozoite in the skin

When an infected female anopheline mosquito bite humans or primates, sporozoites are introduced with the saliva into the vascular tissues of the skin. Within one minute, the motile sporozoites pass through the capillary wall and enter the blood stream [23]. Whiles in circulation the sporozoites moves quickly to invade the parenchymal cells of the liver within 40 minutes [24].

Liver stage malaria

After a successful invasion into the hepatocyte, a single parasite undergoes mitosis to produce 10,000 to 20,000 merozoites within 7-10 days period [25]. The enlarged hepatocyte called schizonts burst to release its content (merozoites) into circulation [23]. The liver phase of the life cycle is not associated with clinical signs and symptoms of malaria, yet permits the parasite to replicate [23].

Asexual erythrocytic cycle

When the merozoites are out from hepatocytes, they invade Red Blood Cells (RBCs) and enter into the asexual erythrocytic cycle. At this point, the parasites (trophozoites) grow and utilize the RBC contents as food. The merozoites grows and develop into a ring or early trophozoite within the erythrocyte. The early or ring trophozoites now develop into a mature trophozoite that undergoes asexual multiplication to form numerous merozoites in the erythrocyte which is now called schizont. When the erythrocytic schizont ruptures, it releases the merozoites which then invade more erythrocytes, thereby completing the erythrocytic cycle. Some of the parasites also differentiates into male and female gametocytes, which are taken up by female anopheline mosquito during blood meal.

Transmission back to mosquitoes

Once the gametocyte is inside the mosquito midgut, the temperature increases and pH changes, initiating gametogenesis and fertilization leading to the formation of motile diploid ookinetes that leave the blood meal bolus and cross the midgut epithelium to become a sessile oocyst. More than 10-14 days old sporozoite develops inside the oocyst by means of mitosis, and these escape through an enzymatic process into the mosquito body cavity. The sporozoites circulate by means of the haemolymph and attaches onto the basal lamina of the mosquito salivary gland, prepared for presentation into the next host [23] (Figure 1).